Spinal implant and integration plate for optimizing vertebral endplate contact load-bearing edges

ABSTRACT

An interbody spinal implant including a body and an integration plate having a top surface, a bottom surface, opposing lateral sides, opposing anterior and posterior portions, and a substantially hollow center in communication with a vertical aperture. The body is recessed in a way that portions of the integration plate protrude above the top and/or bottom surface of the body to enhance the resistance of the implant to expulsion from the intervertebral space.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/571,693, filed Aug. 10, 2012, which is a continuation-in-part of U.S.patent application Ser. No. 12/151,198, filed on May 5, 2008, issued asU.S. Pat. No. 8,262,737 on Sep. 11, 2012, which is acontinuation-in-part of U.S. patent application Ser. No. 11/123,359,filed on May 6, 2005, and issued as U.S. Pat. No. 7,662,186 on Feb. 16,2010. The contents of all prior applications are incorporated byreference in this document, in their entirety and for all purposes.

FIELD OF THE INVENTION

The invention relates generally to interbody spinal implants and methodsof using such implants and, more particularly, to an implant including aprotruding edge on one or more of its anterior, posterior or lateralportions to both bear some load force (e.g., keep some of the spinalload forces off of the body of the implant) and enhance resistance toexpulsion. The anti-expulsion edge may be comprised on the top surfaceof one or more integration plates affixed to the implant body.

BACKGROUND OF THE INVENTION

In the simplest terms, the spine is a column made of vertebrae anddiscs. The vertebrae provide the support and structure of the spinewhile the spinal discs, located between the vertebrae, act as cushionsor “shock absorbers.” These discs also contribute to the flexibility andmotion of the spinal column. Over time, the discs may become diseased orinfected, may develop deformities such as tears or cracks, or may simplylose structural integrity (e.g., the discs may bulge or flatten).Impaired discs can affect the anatomical functions of the vertebrae, dueto the resultant lack of proper biomechanical support, and are oftenassociated with chronic back pain.

Several surgical techniques have been developed to address spinaldefects, such as disc degeneration and deformity. Spinal fusion hasbecome a recognized surgical procedure for mitigating back pain byrestoring biomechanical and anatomical integrity to the spine. Spinalfusion techniques involve the removal, or partial removal, of at leastone intervertebral disc and preparation of the disc space for receivingan implant by shaping the exposed vertebral endplates. An implant isthen inserted between the opposing endplates.

Several interbody implant systems have been introduced to facilitateinterbody fusion. Traditional threaded implants involve at least twocylindrical bodies, each typically packed with bone graft material,surgically placed on opposite sides of the mid-sagittal plane throughpre-tapped holes within the intervertebral disc space. This location isnot the preferable seating position for an implant system, however,because only a relatively small portion of the vertebral endplate iscontacted by these cylindrical implants. Accordingly, these implantbodies will likely contact the softer cancellous bone rather than thestronger cortical bone, or apophyseal rim, of the vertebral endplate.The seating of these threaded cylindrical implants may also compromisebiomechanical integrity by reducing the area in which to distributemechanical forces, thus increasing the apparent stress experienced byboth the implant and vertebrae. Still further, a substantial risk ofimplant subsidence (defined as sinking or settling) into the softercancellous bone of the vertebral body may arise from such improperseating.

In contrast, open ring-shaped cage implant systems are generally shapedto mimic the anatomical contour of the vertebral body. Traditionalring-shaped cages are generally comprised of allograft bone material,however, harvested from the human femur. Such allograft bone materialrestricts the usable size and shape of the resultant implant. Forexample, many of these femoral ring-shaped cages generally have amedial-lateral width of less than 25 mm. Therefore, these cages may notbe of a sufficient size to contact the strong cortical bone, orapophyseal rim, of the vertebral endplate. These size-limited implantsystems may also poorly accommodate related instrumentation such asdrivers, reamers, distractors, and the like. For example, these implantsystems may lack sufficient structural integrity to withstand repeatedimpact and may fracture during implantation. Still further, othertraditional non-allograft ring-shaped cage systems may be size-limiteddue to varied and complex supplemental implant instrumentation which mayobstruct the disc space while requiring greater exposure of theoperating space. These supplemental implant instrumentation systems alsogenerally increase the instrument load upon the surgeon.

The surgical procedure corresponding to an implant system shouldpreserve as much vertebral endplate bone surface as possible byminimizing the amount of bone removed. This vertebral endplate bonesurface, or subchondral bone, is generally much stronger than theunderlying cancellous bone. Preservation of the endplate bone stockensures biomechanical integrity of the endplates and minimizes the riskof implant subsidence. Thus, proper interbody implant design shouldprovide for optimal seating of the implant while utilizing the maximumamount of available supporting vertebral bone stock.

Nevertheless, traditional implantation practices often do not preservecritical bone structures such as vertebral endplates during the surgicalprocedure. In some cases, the implant devices themselves necessitateremoval of bone and were not designed or implanted with the intent topreserve critical bone structures during or after implantation.

In summary, at least ten, separate challenges can be identified asinherent in traditional anterior spinal fusion devices. Such challengesinclude: (1) end-plate preparation; (2) implant difficulty; (3)materials of construction; (4) implant expulsion; (5) implantsubsidence; (6) insufficient room for bone graft; (7) stress shielding;(8) lack of implant incorporation with vertebral bone; (9) limitationson radiographic visualization; and (10) cost of manufacture andinventory.

SUMMARY OF THE INVENTION

The invention is directed to interbody spinal implants and to methods ofusing such implants. The implants can be inserted, using methods of theinvention, from a variety of vantages, including anterior,antero-lateral, and lateral implantation. The spinal implant ispreferably adapted to be inserted into a prepared disc space via aprocedure which does not destroy the vertebral end-plates, or contactsthe vertebral end-plates only peripherally, allowing the intactvertebral end-plates to deflect like a diaphragm under axial compressiveloads generated due to physiologic activities and pressurize the bonegraft material disposed inside the spinal implant.

An implant preferably comprises a body having a top surface, a bottomsurface, opposing lateral sides, opposing anterior and posteriorportions, a substantially hollow center, and a single vertical apertureextending from the top surface to the bottom surface. The verticalaperture comprises a shape, dimensions, and position on the top surfaceand the bottom surface of the implant body, and the shape, dimensions,and position define a transverse rim on the top surface and on thebottom surface of the body. The rim includes an anterior section, aposterior section, a first lateral section, and a second lateralsection. The shape, dimensions, and position of the vertical aperturecause a particular amount of the load force caused by movement orflexing of a vertebrae to be distributed to one or more of the anteriorsection, posterior section, first lateral section, or second lateralsection of the transverse rim. As well, the shape, dimensions, andposition of the vertical aperture cause a particular amount of said loadforce to be distributed to a bone graft material disposed in thesubstantially hollow center and in the aperture. The apportionment ofthe load force distribution may be controlled, at least in part, by theplacement and orientation of the implant in the intervertebral space.The distribution, therefore, may be according to a desired amount.

In general, an implant comprises a body comprising a top surfacecomprising an anterior section, a posterior section, and opposinglateral sections, as well as a bottom surface comprising an anteriorsection, a posterior section, and opposing lateral sections. The bodyalso comprises opposing lateral sides, opposing anterior and posteriorportions, a substantially hollow center, and a single vertical apertureextending from the top surface to the bottom surface.

The implant also preferably comprises at least one integration plate. Anintegration plate may be affixed to the top surface of the body, thebottom surface of the body, or both the top surface and the bottomsurface of the body. The integration plate comprises a top surfacecomprising an anterior section, a posterior section, opposing lateralsections, and a roughened surface topography adapted to grip bone andinhibit migration of the implant, as well as a bottom surface comprisingan anterior section, a posterior section, and opposing lateral sections.The integration plate also comprises opposing lateral sides, opposinganterior and posterior portions, and a single vertical apertureextending from the top surface to the bottom surface of the firstintegration plate and aligning with the single vertical aperture of thebody.

In some aspects, at least a portion of the anterior section of the topsurface of the body is recessed to a first depth, and at least a portionof the posterior section of the top surface of the body is recessed to asecond depth that is less than the first depth. The anterior section ofthe bottom surface of the integration plate is inserted into therecessed portion of the anterior section of the top surface of the bodyand the posterior section of the bottom surface of the integration plateis inserted into the recessed portion of the posterior section of thetop surface of the body. Thus, the anterior section of the bottomsurface of the integration plate aligns with the anterior section of thetop surface of the body to facilitate the connection between the bodyand the integration plate. As a result of the different recessed depths,when the integration plate is joined with the body, the posteriorsection of the top surface of the integration plate protrudes above thehorizontal plane of the top surface of the body. In aspects where theimplant includes an integration plate on the bottom surface of the body(in addition to or in lieu of an integration plate on the top surface ofthe body), the bottom surface of the implant would be have the samerecessed configuration, appropriate for the orientation of the bottom.In this case, however, the posterior section of the top surface of theintegration plate on the bottom of the body will protrude below (e.g.,downward) the horizontal plane of the bottom surface of the body.

In some aspects, at least a portion of the posterior section of the topsurface of the body is recessed to a first depth, and at least a portionof the anterior section of the top surface of the body is recessed to asecond depth that is less than the first depth. The posterior section ofthe bottom surface of the integration plate is inserted into therecessed portion of the posterior section of the top surface of the bodyand the anterior section of the bottom surface of the integration plateis inserted into the recessed portion of the anterior section of the topsurface of the body. Thus, the posterior section of the bottom surfaceof the integration plate aligns with the posterior section of the topsurface of the body to facilitate the connection between the body andthe integration plate. As a result of the different recessed depths,when the integration plate is joined with the body, the anterior sectionof the top surface of the integration plate protrudes above thehorizontal plane of the top surface of the body. In aspects where theimplant includes an integration plate on the bottom surface of the body(in addition to or in lieu of an integration plate on the top surface ofthe body), the bottom surface of the implant would be have the samerecessed configuration, appropriate for the orientation of the bottom.In this case, however, the anterior section of the top surface of theintegration plate on the bottom of the body will protrude below (e.g.,downward) the horizontal plane of the bottom surface of the body.

In some aspects, at least a portion of one of the lateral sections ofthe top surface of the body is recessed to a first depth, and at least aportion of the opposing lateral section of the top surface of the bodyis recessed to a second depth that is greater than the first depth. Oneof the lateral sections of the bottom surface of the integration plateis inserted into the lateral section of the top surface of the bodyrecessed to the first depth, and the opposing lateral section of thebottom surface of the integration plate is inserted into the lateralsection of the top surface of the body recessed to the second depth.Thus, the lateral sections of the bottom surface of the integrationplate align with the lateral sections of the top surface of the body tofacilitate the connection between the body and the integration plate. Asa result of the different recessed depths, when the integration plate isjoined with the body, one of the lateral sections of the top surface ofthe integration plate protrudes above the horizontal plane of the topsurface of the body, and in particular, the protruding lateral sectionon the top surface is the lateral section that is on the same side as(e.g., corresponds to) the lateral section of the bottom surface of theintegration plate inserted into the lateral section of the top surfaceof the body recessed to the first depth. In aspects where the implantincludes an integration plate on the bottom surface of the body (inaddition to or in lieu of an integration plate on the top surface of thebody), the bottom surface of the implant would be have the same recessedconfiguration, appropriate for the orientation of the bottom. In thiscase, however, the lateral section of the top surface of the integrationplate on the bottom of the body will protrude below (e.g., downward) thehorizontal plane of the bottom surface of the body.

The implant may comprise a lordotic angle adapted to facilitatealignment of the spine. At least one of the anterior, posterior, oropposing lateral sections of the top surface of the integration platemay comprise an anti-expulsion edge to resist pullout of the implantfrom the spine of a patient into which the implant has been implanted.The anti-expulsion edge may comprise a blade.

The substantially hollow portion of the body and the vertical apertureof the body and the vertical aperture of the integration plate maycontain a bone graft material adapted to facilitate the formation of asolid fusion column within the spine. The bone graft material may becancellous autograft bone, allograft bone, demineralized bone matrix(DBM), porous synthetic bone graft substitute, bone morphogenic protein(BMP), or a combination thereof. The body may comprise a wall closing atleast one of the opposing anterior and posterior portions of the bodyfor containing the bone graft material.

The implant body and/or the integration plate may be fabricated from ametal. A preferred metal is titanium. The implant body may be fabricatedfrom a non-metallic material, non-limiting examples of which includepolyetherether-ketone, hedrocel, ultra-high molecular weightpolyethylene, and combinations thereof. The implant body may befabricated from both a metal and a non-metallic material, including acomposite thereof. For example, a composite may be formed, in part, oftitanium and, in part, of polyetherether-ketone, hedrocel, ultra-highmolecular weight polyethylene, or combinations thereof.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary, but are notrestrictive, of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is best understood from the following detailed descriptionwhen read in connection with the accompanying drawing. It is emphasizedthat, according to common practice, the various features of the drawingare not to scale. On the contrary, the dimensions of the variousfeatures are arbitrarily expanded or reduced for clarity. Included inthe drawing are the following figures:

FIG. 1A shows a perspective view of an embodiment of the interbodyspinal implant having a generally oval shape and roughened surfacetopography on the top surface;

FIG. 1B shows a top view of the first embodiment of the interbody spinalimplant illustrated in FIG. 1A;

FIG. 2 shows a perspective view from the front of another embodiment ofthe interbody spinal implant according to the invention;

FIG. 3 shows a perspective view from the rear of the embodiment of theinterbody spinal implant illustrated in FIG. 2;

FIG. 4 shows a perspective view from the front of yet another embodimentof the interbody spinal implant according to the invention;

FIG. 5 shows a perspective view from the rear of the embodiment of theinterbody spinal implant illustrated in FIG. 4 highlighting analternative transverse aperture;

FIG. 6 shows a perspective view of another embodiment of the interbodyspinal implant having a generally oval shape and being especially welladapted for use in a cervical spine surgical procedure;

FIG. 7 shows a perspective view of an implant having a generally boxshape;

FIG. 8 shows an exploded view of a generally oval-shaped implant with anintegration plate;

FIG. 9 shows an exploded view of a curved implant with an integrationplate;

FIG. 10 shows an exploded view of a posterior implant with anintegration plate;

FIG. 11 shows an exploded view of a lateral lumbar implant with anintegration plate;

FIG. 12 shows an exploded view of a generally oval-shaped anteriorcervical implant with an integration plate;

FIG. 13A shows an oval-shaped implant with a protruding anti-expulsionedge;

FIG. 13B shows a close-up view of the protruding anti-expulsion edge ofthe implant illustrated in FIG. 13A;

FIG. 13C shows a rectangular-shaped implant with a protrudinganti-expulsion edge oriented toward the posterior portion;

FIG. 13D shows a close-up view of the protruding anti-expulsion edge ofthe implant illustrated in FIG. 183;

FIG. 13E shows a perspective view of a curved-shaped implant with aprotruding anti-expulsion edge oriented toward the posterior portion;

FIG. 13F shows a close-up view of the protruding anti-expulsion edge ofthe implant perspective illustrated in FIG. 13E;

FIG. 13G shows another perspective view of the implant illustrated inFIG. 13E;

FIG. 13H shows a close-up view of the protruding anti-expulsion edge ofthe implant illustrated in FIG. 13G;

FIG. 13I shows a perspective view of a rectangular-shaped implant with aprotruding anti-expulsion edge oriented toward one of the lateral sides;

FIG. 13J shows another perspective view of the implant illustrated inFIG. 13I;

FIG. 13K shows a close-up view of the protruding anti-expulsion edge ofthe implant illustrated in FIG. 13L;

FIG. 13L shows a perspective view of a cervical implant with aprotruding anti-expulsion edge;

FIG. 13M shows a close-up view of the protruding anti-expulsion edge ofthe implant illustrated in FIG. 13L;

FIG. 13N shows an oval-shaped implant with an integration platesubstantially flush with the horizontal plane of the top surface of theimplant;

FIG. 14A shows an example of an integration plate lordotic angle;

FIG. 14B shows an example of an anti-expulsion edge angle.

FIG. 15A shows an oval-shaped implant positioned on the vertebralendplate;

FIG. 15B shows an anterior spine perspective of an oval-shaped implantpositioned between an upper and lower vertebrae;

FIG. 15C shows a laterally inserted implant positioned on the vertebralendplate;

FIG. 15D shows an anterior spine perspective of a laterally insertedimplant positioned between an upper and lower vertebrae;

FIG. 16A shows a perspective of two posterior inserted implantspositioned on the vertebral endplate;

FIG. 16B shows a top perspective of two posterior inserted implantspositioned on the vertebral endplate;

FIG. 16C shows a perspective of a single posterior inserted implantpositioned at an oblique angle on the vertebral endplate;

FIG. 16D shows a top perspective of a single posterior inserted implantpositioned at an oblique angle on the vertebral endplate;

FIG. 16E shows a perspective of a transforaminal curved implantpositioned proximal to the anterior end of a vertebral endplate;

FIG. 16F shows a top perspective of a transforaminal curved implantpositioned proximal to the anterior end of a vertebral endplate;

FIG. 17A shows a top view of an embodiment of a vertical aperture for anoval-shaped implant;

FIG. 17B shows a top view of another embodiment of a vertical aperturefor an oval-shaped implant;

FIG. 17C shows a top view of another embodiment of a vertical aperturefor an oval-shaped implant;

FIG. 17D shows a top view of another embodiment of a vertical aperturefor an oval-shaped implant;

FIG. 18A shows a top view of an embodiment of a vertical aperture for aposterior implant;

FIG. 18B shows a top view of another embodiment of a vertical aperturefor a posterior implant;

FIG. 18C shows a top view of another embodiment of a vertical aperturefor a posterior implant;

FIG. 18D shows a top view of another embodiment of a vertical aperturefor a posterior implant;

FIG. 19A shows a top view of an embodiment of a vertical aperture for acurved implant;

FIG. 19B shows a top view of another embodiment of a vertical aperturefor a curved implant;

FIG. 19C shows a top view of another embodiment of a vertical aperturefor a curved implant;

FIG. 19D shows a top view of another embodiment of a vertical aperturefor a curved implant;

FIG. 20A shows a top view of an embodiment of a vertical aperture for acervical implant;

FIG. 20B shows a top view of another embodiment of a vertical aperturefor a cervical implant;

FIG. 20C shows a top view of another embodiment of a vertical aperturefor a cervical implant;

FIG. 20D shows a top view of another embodiment of a vertical aperturefor a cervical implant;

FIG. 21A shows a top view of an embodiment of a vertical aperture for alateral implant;

FIG. 21B shows a top view of another embodiment of a vertical aperturefor a lateral implant;

FIG. 21C shows a top view of another embodiment of a vertical aperturefor a lateral implant; and

FIG. 21D shows a top view of another embodiment of a vertical aperturefor a lateral implant.

DETAILED DESCRIPTION OF THE INVENTION

Certain embodiments of the invention may be especially suited forplacement between adjacent human vertebral bodies. The implants of theinvention may be used in procedures such as Anterior Lumbar InterbodyFusion (ALIF), Posterior Lumbar Interbody Fusion (PLIF), TransforaminalLumbar Interbody Fusion (TLIF), and cervical fusion. Certain embodimentsdo not extend beyond the outer dimensions of the vertebral bodies.

The ability to achieve spinal fusion is directly related to theavailable vascular contact area over which fusion is desired, thequality and quantity of the fusion mass, and the stability of theinterbody spinal implant. Interbody spinal implants, as now taught,allow for improved seating over the apophyseal rim of the vertebralbody. Still further, interbody spinal implants, as now taught, betterutilize this vital surface area over which fusion may occur and maybetter bear the considerable biomechanical loads presented through thespinal column with minimal interference with other anatomical orneurological spinal structures. Even further, interbody spinal implants,according to certain aspects of the invention, allow for improvedvisualization of implant seating and fusion assessment. Interbody spinalimplants, as now taught, may also facilitate osteointegration with thesurrounding living bone.

Anterior interbody spinal implants in accordance with certain aspects ofthe invention can be preferably made of a durable material such asstainless steel, stainless steel alloy, titanium, or titanium alloy, butcan also be made of other durable materials such as, but not limited to,polymeric, ceramic, and composite materials. For example, certainembodiments of the invention may be comprised of a biocompatible,polymeric matrix reinforced with bioactive fillers, fibers, or both.Certain embodiments of the invention may be comprised of urethanedimethacrylate (DUDMA)/tri-ethylene glycol dimethacrylate (TEDGMA)blended resin and a plurality of fillers and fibers including bioactivefillers and E-glass fibers. Durable materials may also consist of anynumber of pure metals, metal alloys, or both. Titanium and its alloysare generally preferred for certain embodiments of the invention due totheir acceptable, and desirable, strength and biocompatibility. In thismanner, certain embodiments of the present interbody spinal implant mayhave improved structural integrity and may better resist fracture duringimplantation by impact. Interbody spinal implants, as now taught, maytherefore be used as a distractor during implantation.

Referring now to the drawing, in which like reference numbers refer tolike elements throughout the various figures that comprise the drawing,FIG. 1 shows a perspective view of a first embodiment of the interbodyspinal implant 1 especially well adapted for use in an ALIF procedure.

The interbody spinal implant 1 includes a body having a top surface 10,a bottom surface 20, opposing lateral sides 30, and opposing anterior 40and posterior 50 portions. One or both of the top surface 10 and thebottom surface 20 has a roughened topography 80. The roughenedtopography 80, however, is distinct from the teeth provided on thesurfaces of some conventional devices.

In some aspects, the interbody spinal implant 1 is substantially hollowand has a generally oval-shaped transverse cross-sectional area withsmooth, rounded, or both smooth and rounded lateral sides 30 andposterior-lateral corners 52. A substantially hollow implant 1 includesan implant 1 having at least about 33% of the interior volume of theimplant 1 vacant. The implant 1 includes at least one vertical aperture60 that extends the entire height of the implant body.

It is generally believed that the surface of an implant determines itsultimate ability to integrate into the surrounding living bone. Withoutbeing limited to any particular theory or mechanism of action, it isbelieved that the cumulative effects of at least implant composition,implant surface energy, and implant surface roughness play a major rolein the biological response to, and osteointegration of, an implantdevice. Thus, implant fixation may depend, at least in part, on theattachment and proliferation of osteoblasts and like-functioning cellsupon the implant surface.

It is believed that cells attach more readily to relatively roughsurfaces rather than smooth surfaces. In this manner, a surface may bebioactive due to its ability to facilitate cellular attachment andosteointegration. The surface roughened topography 80 may better promotethe osteointegration of the implant 1. The surface roughened topography80 may also better grip the vertebral endplate surfaces and inhibitimplant migration of the implant 1 upon placement and seating in apatient.

Accordingly, the implant 1 further includes the roughened topography 80on at least a portion of its top 10 and bottom 20 surfaces for grippingadjacent bone and inhibiting migration of the implant 1. FIG. 1 showsroughened topography 80 on an embodiment of the implant 1.

The roughened topography 80 may be obtained through a variety oftechniques including, without limitation, chemical etching, shotpeening, plasma etching, laser etching, or abrasive blasting (such assand or grit blasting). In at least one embodiment, the interbody spinalimplant 1 may be comprised of titanium, or a titanium alloy, having thesurface roughened topography 80. The surfaces of the implant 1 arepreferably bioactive.

In a preferred embodiment of the invention, the roughened topography 80is obtained via the repetitive masking and chemical or electrochemicalmilling processes described in U.S. Pat. No. 5,258,098; No. 5,507,815;No. 5,922,029; and No. 6,193,762. Each of these patents is incorporatedin this document by reference. Where the invention employs chemicaletching, the surface is prepared through an etching process whichutilizes the random application of a maskant and subsequent etching ofthe metallic substrate in areas unprotected by the maskant. This etchingprocess is repeated a number of times as necessitated by the amount andnature of the irregularities required for any particular application.Control of the strength of the etchant material, the temperature atwhich the etching process takes place, and the time allotted for theetching process allow fine control over the resulting surface producedby the process. The number of repetitions of the etching process canalso be used to control the surface features.

By way of example, an etchant mixture of nitric acid (HNO.sub.3) andhydrofluoric (HF) acid may be repeatedly applied to a titanium surfaceto produce an average etch depth of about 0.53 mm. Interbody spinalimplants 1, in accordance with some preferred embodiments of theinvention, may be comprised of titanium, or a titanium alloy, having anaverage surface roughness of about 100 .mu.m. Surface roughness may bemeasured using a laser profilometer or other standard instrumentation.

In another example, chemical modification of the titanium implantsurfaces can be achieved using HF and a combination of hydrochloric acidand sulfuric acid (HCl/H.sub.2SO.sub.4). In a dual acid etching process,the first exposure is to HF and the second is to HCl/H.sub.2SO.sub.4.Chemical acid etching alone of the titanium implant surface has thepotential to greatly enhance osteointegration without adding particulatematter (e.g., hydroxyapatite) or embedding surface contaminants (e.g.,grit particles) and this surface can be bioactive, for example, byinducing or supporting bone formation by cellular reactions.

The implant 1 may be shaped to reduce the risk of subsidence, andimprove stability, by maximizing contact with the apophyseal rim ofvertebral endplates. Embodiments may be provided in a variety ofanatomical footprints having a medial-lateral width ranging from about32 mm to about 44 mm. An interbody spinal implant 1 generally does notrequire extensive supplemental or obstructive implant instrumentation tomaintain the prepared disc space during implantation. Thus, theinterbody spinal implant 1 and associated implantation methods allow forlarger-sized implants as compared with other size-limited interbodyspinal implants known in the art. This advantage allows for greatermedial-lateral width and correspondingly greater contact with theapophyseal rim. The implant 1 may also include an anti-expulsion edge 8as described in more detail below.

As illustrated in FIG. 1, the implant 1 has an opening 90 in theanterior portion 40. In one embodiment the posterior portion 50 has asimilarly shaped opening 90. In some aspects, only the anterior portion40 has the opening 90 while the posterior portion 50 has an alternativeopening 92 (which may have a size and shape different from the opening90).

The opening 90 has a number of functions. One function is to facilitatemanipulation of the implant 1 by the caretaker. Thus, the caretaker mayinsert a surgical tool into the opening 90 and, through the engagementbetween the surgical tool and the opening 90, manipulate the implant 1.The opening 90 may be threaded to enhance the engagement.

The implant 1 may further include at least one transverse aperture 70that extends the entire transverse length of the implant body. The atleast one transverse aperture 70 may provide improved visibility of theimplant 1 during surgical procedures to ensure proper implant placementand seating, and may also improve post-operative assessment of implantfusion. Still further, the substantially hollow area defined by theimplant 1 may be filled with cancellous autograft bone, allograft bone,DBM, porous synthetic bone graft substitute, BMP, or combinations ofthese materials (collectively, bone graft materials), to facilitate theformation of a solid fusion column within the spine of a patient.

Certain embodiments of the invention are particularly suited for useduring interbody spinal implant procedures (or vertebral bodyreplacement procedures) and may act as a final distractor duringimplantation, thus minimizing the instrument load upon the surgeon. Forexample, in such a surgical procedure, the spine may first be exposedvia an anterior approach and the center of the disc space identified.The disc space is then initially prepared for implant insertion byremoving vertebral cartilage. Soft tissue and residual cartilage maythen also be removed from the vertebral endplates.

Vertebral distraction may be performed using trials of various-sizedembodiments of the interbody spinal implant 1. The determinatively sizedinterbody implant 1 may then be inserted in the prepared disc space forfinal placement. The distraction procedure and final insertion may alsobe performed under fluoroscopic guidance. The substantially hollow areawithin the implant body may optionally be filled, at least partially,with bone fusion-enabling materials such as, without limitation,cancellous autograft bone, allograft bone, DBM, porous synthetic bonegraft substitute, BMP, or combinations of those materials. Such bonefusion-enabling material may be delivered to the interior of theinterbody spinal implant 1 using a delivery device mated with theopening 90 in the anterior portion 40 of the implant 1. The interbodyspinal implant 1 may be generally larger than those currently known inthe art, and therefore have a correspondingly larger hollow area whichmay deliver larger volumes of fusion-enabling bone graft material. Thebone graft material may be delivered such that it fills the full volume,or less than the full volume, of the implant interior and surroundingdisc space appropriately.

As noted above, FIG. 1 shows a perspective view of one embodiment of theinvention, the interbody spinal implant 1, which is especially welladapted for use in an ALIF procedure. Other embodiments of the inventionare better suited for PLIF, TLIF, or cervical fusion procedures.Specifically, FIGS. 2 and 3 show perspective views, from the front andrear, respectively, of an embodiment of an interbody spinal implant 101especially well adapted for use in a PLIF procedure. The interbodyspinal implant 101 includes a body having a top surface 110, a bottomsurface 120, opposing lateral sides 130, and opposing anterior 140 andposterior 150 portions. One or both of the top surface 110 and thebottom surface 120 has a roughened topography 180 for gripping adjacentbone and inhibiting migration of the implant 101.

Certain embodiments of the interbody spinal implant 101 aresubstantially hollow and have a generally rectangular shape with smooth,rounded, or both smooth and rounded lateral sides and anterior-lateralcorners. As best shown in FIG. 3, the anterior portion 140 may have atapered nose 142 to facilitate insertion of the implant 101. To furtherfacilitate insertion, the implant 101 has chamfers 106 at the corners ofits posterior portion 150. The chamfers 106 prevent the implant 101 fromcatching upon insertion, risking potential damage such as severednerves, while still permitting the implant 101 to have an anti-expulsionedge 108.

The implant 101 includes at least one vertical aperture 160 that extendsthe entire height of the implant body. The vertical aperture 160 furtherdefines a transverse rim 200.

As illustrated in FIG. 2, the implant 101 has an opening 190 in theposterior portion 150. The opening 190 has a number of functions. Onefunction is to facilitate manipulation of the implant 101 by thecaretaker. Thus, the caretaker may insert a surgical tool into theopening 190 and, through the engagement between the surgical tool andthe opening 190, manipulate the implant 101. The opening 190 may bethreaded to enhance the engagement.

The implant 101 may also have an Implant Holding Feature (IHF) 194instead of or in addition to the opening 190. As illustrated in FIG. 2,the IHF 194 is located proximate the opening 190 in the posteriorportion 150. In this particular example, the IHF 194 is a U-shapednotch. Like the opening 190, the IHF 194 has a number of functions, oneof which is to facilitate manipulation of the implant 101 by thecaretaker. Other functions of the opening 190 and the IHF 194 are toincrease visibility of the implant 101 during surgical procedures and toenhance engagement between bone graft material and adjacent bone.

The implant 101 may further include at least one transverse aperture170. Like the vertical aperture 160, the size and shape of thetransverse aperture 170 are carefully chosen (and predetermined) toachieve a preferable design tradeoff for the particular applicationenvisioned for the implant 101. Specifically, the transverse aperture170 should have minimal dimensions to maximize the strength andstructural integrity of the implant 101. On the other hand, thetransverse aperture 70 should have maximum dimensions to (a) improve thevisibility of the implant 101 during surgical procedures to ensureproper implant placement and seating, and to improve post-operativeassessment of implant fusion, and (b) to facilitate engagement betweenbone graft material and adjacent bone. The substantially hollow areadefined by the implant 101 may be filled with bone graft materials tofacilitate the formation of a solid fusion column within the spine of apatient.

As shown in FIGS. 2 and 3, the transverse aperture 170 extends theentire transverse length of the implant body and nearly the entireheight of the implant body. Thus, the size and shape of the transverseaperture 170 approach the maximum possible dimensions for the transverseaperture 170.

The transverse aperture 170 may be broken into two, separate sections byan intermediate wall 172. The section of the transverse aperture 170proximate the IHF 194 is substantially rectangular in shape; the othersection of the transverse aperture 170 has the shape of a curved arch.Other shapes and dimensions are suitable for the transverse aperture170. In particular, all edges of the transverse aperture 170 may berounded, smooth, or both. The intermediate wall 172 may be made of thesame material as the remainder of the implant 101 (e.g., metal), or itmay be made of another material (e.g., PEEK) to form a composite implant101. The intermediate wall 172 may offer one or more of severaladvantages, including reinforcement of the implant 101 and improved bonegraft containment.

The embodiment of the invention illustrated in FIGS. 2 and 3 isespecially well suited for a PLIF surgical procedure. TLIF surgery isdone through the posterior (rear) part of the spine and is essentiallylike an extended PLIF procedure. The TLIF procedure was developed inresponse to some of the technical problems encountered with a PLIFprocedure. The main difference between the two spine fusion proceduresis that the TLIF approach to the disc space is expanded by removing oneentire facet joint; a PLIF procedure is usually done on both sides byonly taking a portion of each of the paired facet joints.

By removing the entire facet joint, visualization into the disc space isimproved and more disc material can be removed. Such removal should alsoprovide for less nerve retraction. Because one entire facet is removed,the TLIF procedure is only done on one side: removing the facet jointson both sides of the spine would result in too much instability. Withincreased visualization and room for dissection, one or both of a largerimplant and more bone graft can be used in the TLIF procedure.Theoretically, these advantages can allow the spine surgeon to distractthe disc space more and realign the spine better (re-establish thenormal lumbar lordosis).

Although the TLIF procedure offers some improvements over a PLIFprocedure, the anterior approach in most cases still provides the bestvisualization, most surface area for healing, and the best reduction ofany of the approaches to the disc space. These advantages must beweighed, however, against the increased morbidity (e.g., unwantedaftereffects and postoperative discomfort) of a second incision.Probably the biggest determinate in how the disc space is approached isthe comfort level that the spine surgeon has with an anterior approachfor the spine fusion surgery. Not all spine surgeons are comfortablewith operating around the great vessels (aorta and vena cava) or haveaccess to a skilled vascular surgeon to help them with the approach.Therefore, choosing one of the posterior approaches for the spine fusionsurgery is often a more practical solution.

The embodiment of the invention illustrated in FIGS. 4 and 5 isespecially well suited when the spine surgeon elects a TLIF procedure.Many of the features of the implant 101 a illustrated in FIGS. 4 and 5are the same as those of the implant 101 illustrated in FIGS. 2 and 3.Therefore, these features are given the same reference numbers, with theaddition of the letter “a,” and are not described further.

There are several differences, however, between the two embodiments. Forexample, unlike the substantially rectangular shape of the implant 101,the implant 101 a has a curved shape. Further, the chamfers 106 andanti-expulsion edge 108 of the implant 101 are replaced by curves orrounded edges for the implant 101 a. Still further, the TLIF procedureoften permits use of a larger implant 101 a which, in turn, may affectthe size and shape of the predetermined vertical aperture 160 a.

The substantially constant 9 mm width of the transverse rim 200 of theimplant 101 is replaced with a larger, curved transverse rim 200 a. Thewidth of the transverse rim 200 a is 9 mm in the regions adjacent theanterior 140 a and posterior 150 a portions. That width graduallyincreases to 11 mm, however, near the center of the transverse rim 200a. The additional real estate provided by the transverse rim 200 a(relative to the transverse rim 200) allows the shape of the verticalaperture 160 a to change, in cross section, from approximating afootball to approximating a boomerang.

The implant 101 a may also have a lordotic angle to facilitatealignment. The lateral side 130 a depicted at the top of the implant 101a is preferably generally greater in height than the opposing lateralside 130 a. Therefore, the implant 101 a may better compensate for thegenerally less supportive bone found in certain regions of the vertebralendplate.

As shown in FIG. 4, the transverse aperture 170 a extends the entiretransverse length of the implant body and nearly the entire height ofthe implant body. FIG. 5 highlights an alternative transverse aperture170 a. As illustrated in FIG. 5, the transverse aperture 170 a is brokeninto two, separate sections by an intermediate wall 172 a. Thus, thedimensions of the transverse aperture 170 a shown in FIG. 5 are muchsmaller than those for the transverse aperture 170 a shown in FIG. 4.The two sections of the alternative transverse aperture 170 a are eachillustrated as substantially rectangular in shape and extending nearlythe entire height of the implant body; other sizes and shapes arepossible for one or both sections of the alternative transverse aperture170 a.

The intermediate wall 172 a may be made of the same material as theremainder of the implant 101 a (e.g., metal), or it may be made ofanother material (e.g., PEEK) to form a composite implant 101 a. It isalso possible to extend the intermediate wall 172 a, whether made ofmetal, PEEK, ultra-high molecular weight polyethylene (UHMWPE), oranother material, to eliminate entirely the transverse aperture 170 a.Given the reinforcement function of the intermediate wall 172 a, thelength of the vertical aperture 160 a can be extended (as shown in FIG.5) beyond the top surface 110 a and into the anterior portion 140 a ofthe implant 101 a.

The top surface 110 a of the implant 101 a need not include theroughened topography 180 a. This difference permits the implant 101 a,at least for certain applications, to be made entirely of a non-metalmaterial. Suitable materials of construction for the implant 101 a ofsuch a design (which would not be a composite) include PEEK, hedrocel,UHMWPE, other radiolucent soft plastics, and additional materials aswould be known to an artisan.

The embodiments of the invention described above are best suited for oneor more of the ALIF, PLIF, and TLIF surgical procedures. Anotherembodiment of the invention is better suited for cervical fusionprocedures. This embodiment is illustrated in FIGS. 6 and 7 as theinterbody spinal implant 201.

Because there is not a lot of disc material between the vertebral bodiesin the cervical spine, the discs are usually not very large. The spaceavailable for the nerves is also not that great, however, which meansthat even a small cervical disc herniation may impinge on the nerve andcause significant pain. There is also less mechanical load on the discsin the cervical spine as opposed to the load that exists lower in thespine. Among others, these differences have ramifications for the designof the implant 201.

The implant 201 is generally smaller in size than the other implantembodiments. In addition, the lower mechanical load requirements imposedby the cervical application typically render a composite implantunnecessary. Therefore, the implant 201 is generally made entirely ofmetal (e.g., titanium) and devoid of other materials (e.g., PEEK).

With specific reference to FIG. 6, the implant 201 includes a bodyhaving a top surface 210, a bottom surface 220, opposing lateral sides230, and opposing anterior 240 and posterior 250 portions. One or bothof the top surface 210 and the bottom surface 220 has a roughenedtopography 280 for gripping adjacent bone and inhibiting migration ofthe implant 201. The implant 201 is substantially hollow and has agenerally oval shape with smooth, rounded, or both smooth and roundededges.

The implant 201 includes at least one vertical aperture 260 that extendsthe entire height of the implant body. The vertical aperture 260 furtherdefines a transverse rim 300.

As illustrated in FIG. 6, the implant 201 has an opening 290 in theposterior portion 250. The opening 290 has a number of functions. Onefunction is to facilitate manipulation of the implant 201 by thecaretaker. Thus, the caretaker may insert a surgical tool into theopening 290 and, through the engagement between the surgical tool andthe opening 290, manipulate the implant 201. The opening 290 may bethreaded to enhance the engagement.

The implant 201 may further include at least one transverse aperture270. Like the vertical aperture 260, the size and shape of thetransverse aperture 270 are carefully chosen (and predetermined) toachieve a preferable design tradeoff for the particular applicationenvisioned for the implant 201. For example, as shown in FIG. 6, thetransverse aperture 270 may extend the entire transverse length of theimplant body and nearly the entire height of the implant body. Thus, thesize and shape of the transverse aperture 270 approach the maximumpossible dimensions for the transverse aperture 270.

As illustrated in FIG. 6, the implant 201 may be provided with a solidrear wall 242. The rear wall 242 extends the entire width of the implantbody and nearly the entire height of the implant body. Thus, the rearwall 242 essentially closes the anterior portion 240 of the implant 201.The rear wall 242 may offer one or more of several advantages, includingreinforcement of the implant 201 and improved bone graft containment. Inthe cervical application, it may be important to prevent bone graftmaterial from entering the spinal canal.

Alternative shapes for the implant 201 are possible. As illustrated inFIG. 7, for example, the implant 201 may have a generally box shapewhich gives the implant 201 increased cortical bone coverage. Like theimplant 201 shown in FIG. 6, the implant 201 shown in FIG. 7 has acurved transverse rim 300 in the area of the anterior portion 240. Theshape of the posterior portion 250 of the implant 201 is substantiallyflat, however, and the shape of the transverse rim 300 in the area ofthe posterior portion 250 is substantially square. Thus, the posteriorportion 250 provides a face that can receive impact from a tool, such asa surgical hammer, to force the implant 201 into position.

The implant 201 may also have a lordotic angle to facilitate alignment.As illustrated in FIGS. 6 and 7, the anterior portion 240 is preferablygenerally greater in height than the posterior portion 250. Therefore,the implant 201 may better compensate for the generally less supportivebone found in certain regions of the vertebral endplate. As an example,four degrees of lordosis may be built into the implant 201 to helprestore balance to the spine.

Certain embodiments of the implant 1, 101, 101 a, and 201 are generallyshaped (i.e., made wide) to maximize contact with the apophyseal rim ofthe vertebral endplates. They are designed to be impacted between theendplates, with fixation to the endplates created by an interference fitand annular tension. Thus, the implants 1, 101, 101 a, and 201 areshaped and sized to spare the vertebral endplates and leave intact thehoop stress of the endplates. A wide range of sizes are possible tocapture the apophyseal rim, along with a broad width of the peripheralrim, especially in the posterior region. It is expected that suchdesigns will lead to reduced subsidence. As much as seven degrees oflordosis (or more) may be built into the implants 1, 101, 101 a, and 201to help restore cervical balance.

When endplate-sparing spinal implant 1, 101, 101 a, and 201 seats in thedisc space against the apophyseal rim, it should still allow fordeflection of the endplates like a diaphragm. This means that,regardless of the stiffness of the spinal implant 1, 101, 101 a, and201, the bone graft material inside the spinal implant 1, 101, 101 a,and 201 receives load, leading to healthy fusion. The vertical load inthe human spine is transferred though the peripheral cortex of thevertebral bodies. By implanting an apophyseal-supporting inter-bodyimplant 1, 101, 101 a, and 201, the natural biomechanics may be betterpreserved than for conventional devices. If this is true, the adjacentvertebral bodies should be better preserved by the implant 1, 101, 101a, and 201, hence reducing the risk of adjacent segment issues.

In addition, the dual-acid etched roughened topography 80, 180, 180 a,and 280 of the top surface 30, 130, 130 a, and 230 and the bottomsurface 40, 140, 140 a, and 240 along with the broad surface area ofcontact with the end-plates, is expected to yield a high pull-out forcein comparison to conventional designs. As enhanced by the sharp edges 8and 108, a pull-out strength of up to 3,000 nt may be expected. Theroughened topography 80, 180, 180 a, and 280 creates a biological bondwith the end-plates over time, which should enhance the quality offusion to the bone. Also, the in-growth starts to happen much earlierthan the bony fusion. The center of the implant 1, 101, 101 a, and 201remains open to receive bone graft material and enhance fusion.Therefore, it is possible that patients might be able to achieve a fullactivity level sooner than for conventional designs.

The spinal implant 1, 101, 101 a, and 201 according to the inventionoffers several advantages relative to conventional devices. Suchconventional devices include, among others, ring-shaped cages made ofallograft bone material, threaded titanium cages, and ring-shaped cagesmade of PEEK or carbon fiber.

In some aspects, the implant 1, 101, 101 a, and 201 includes anintegration plate 82, 182, 182 a, and 282, for example, as shown in FIG.8A-FIG. 10 and FIG. 12. In addition, a lateral implant 301 having asubstantially rectangular shape may include an integration plate 382,for example, as shown in FIG. 11. The lateral implant 301 comprises thesame general features as the implant 1, 101, 101 a, and 201, including atop surface 310, a bottom surface 320, lateral sides 330, opposinganterior 340 and posterior 350 portions, an opening 390, as well as atleast one vertical aperture 360 that extends the entire height of theimplant body, and one or more transverse apertures 370 that extend theentire transverse length of the implant body.

The integration plate, shown in the drawings as component 82 (FIG. 8Aand FIG. 8B), 182 (FIG. 10), 182 a (FIG. 9), 382 (FIG. 11), and 282(FIG. 12), respectively, includes the roughened surface topography 80,180, 180 a, 280, and 380, and is connectable to either or both of thetop surface 10, 110, 110 a, 210, and 310 or bottom surface 20, 120, 120a, 220, and 320. The integration plate 82, 182, 182 a, 282, and 382includes a top surface 81, 181, 181 a, 281, and 381; a bottom surface83, 183, 183 a, 283, and 383; an anterior portion 41, 141, 141 a, 241,and 341; a posterior portion 51, 151, 151 a, 251, and 351; and at leastone vertical aperture 61, 161, 161 a, 261, and 361. The anterior portion41, 141, 141 a, 241, and 341 preferably aligns with the anterior portion40, 140, 140 a, 240, and 340 of the main body of the implant 1, 101, 101a, 201, and 301, respectively, and the posterior portion 51, 151, 151 a,251, and 351 aligns with the posterior portion 50, 150, 150 a, 250, and350 of the main body of the implant 1, 101, 101 a, 201, and 301,respectively. The vertical aperture 61, 161, 161 a, 261, and 361preferably aligns with the vertical aperture 60, 160, 160 a, 260, and360 of the main body of the implant 1, 101, 101 a, 201, and 301,respectively. Thus, the integration plate vertical aperture 61, 161, 161a, 261, and 361 and the body vertical aperture 60, 160, 160 a, 260, and360 preferably comprise substantially the same shape.

The top surface 81, 181, 181 a, 281, and 381 of the integration plate82, 182, 182 a, 282, and 382 preferably comprises the roughenedtopography 80, 180, 180 a, 280, and 380. The bottom surface 83, 183, 183a, 283, and 383 of the integration plate 82, 182, 182 a, 282, and 382preferably comprises a reciprocal connector structure, such as aplurality of posts 84, 184, 184 a, 284, and 384 that align with andinsert into a corresponding connector structure such as a plurality ofholes 12, 112, 112 a, 212, and 312 on the top surface 10, 110, 110 a,210, and 310 and/or bottom surface 20, 120, 120 a, 220, and 320 of themain body of the implant 1, 101, 101 a, 201, and 301, respectively, andthus facilitate the connection between the integration plate 82, 182,182 a, 282, and 382 and the main body of the implant 1, 101, 101 a, 201,and 301. Thus, integration plates 82, 182, 182 a, 282, and 382 withdifferent sizes, shapes, or features may be used in connection with theimplant 1, 101, 101 a, 201, and 301, for example, to accommodateattributes of the spine of the patient to which the implant 1, 101, 101a, 201, and 301 is to be implanted. Among these different sizes, shapes,and features are lordotic angles; anti-expulsion edges 8, 108, 108 a,208, and 308; and anti-expulsion angles as described throughout thisspecification.

The implant 1, 101, 101 a, 201, and 301 is configured to receive theintegration plate 82, 182, 182 a, 282, and 382, respectively. Thus, forexample, the top surface 10, 110, 110 a, 210, and 310 and/or bottomsurface 20, 120, 120 a, 220, and 320 of the implant 1, 101, 101 a, 201,and 301 may be recessed, and comprise a plurality of holes 12, 112, 112a, 212, and 312 that mate with the plurality of posts 84, 184, 184 a,284, and 384 on the bottom surface 83, 183, 183 a, 283, and 383 of theintegration plate 82, 182, 182 a, 282, and 382. Thus, the plurality ofposts 84, 184, 184 a, 284, and 384 are inserted into the plurality ofholes 12, 112, 112 a, 212, and 312.

FIG. 8A and FIG. 8B show that the top surface 10 is recessed andcomprises a plurality of holes 12, but the recessed bottom surface 20and its holes 12 are not shown. FIG. 9 shows that the top surface 110 ais recessed and comprises a plurality of holes 112 a, but the recessedbottom surface 120 a and its holes 112 a are not shown. FIG. 10 showsthat the top surface 110 is recessed and comprises a plurality of holes112, but the recessed bottom surface 120 and its holes 112 are notshown. FIG. 11 shows that the top surface 310 is recessed and comprisesa plurality of holes 312, but the recessed bottom surface 320 and itsholes 312 are not shown. FIG. 12 shows that the top surface 210 isrecessed and comprises a plurality of holes 212, but the recessed bottomsurface 220 and its holes 212 are not shown.

The recess comprises a (first) depth D, which in some aspects is uniformthroughout the top surface 10, 110, 110 a, 210, and 310 and/or bottomsurface 20, 120, 120 a, 220, and 320. In some aspects, the recesscomprises a depth D and a second depth D′. For example, implant 1, 101,101 a, 201, and 301 may be recessed to depth D to form the anterior sideof the ridge 11, 111, 111 a, 211, and 311, and recessed at second depthD′ to form the posterior side of the ridge 11, 111, 111 a, 211, and 311,and vice versa. As well, implant 1, 101, 101 a, 201, and 301 may berecessed to depth D to form the one lateral side of the ridge 11, 111,111 a, 211, and 311, and recessed at second depth D′ to form the otherlateral side of the ridge 11, 111, 111 a, 211, and 311.

The top surface 10, 110, 110 a, 210, and 310 and/or bottom surface 20,120, 120 a, 220, and 320 may thus be inclined/declined in the directionof depth D to second depth D′, thereby establishing a slope between thedepth D and second depth D′ points. This slope may be used, for example,to allow an integration plate 82, 182, 182 a, 282, and 382 attached tothe top extend higher at a desired point at the surface of the implant1, 101, 101 a, 201, and 301. For example, the anterior edge 41, 141, 141a, 241, and 341, or the posterior edge 51, 151, 151 a, 251, and 351, orone of the lateral side walls 31, 131, 131 a, 231, and 331 of anintegration plate 82, 182, 182 a, 282, and 382 may extend above thehorizontal plane of the top surface 10, 110, 110 a, 210, and 310 and/orbottom surface 20, 120, 120 a, 220, and 320 of the implant 1, 101, 101a, 201, and 301. The extending portion of the integration plate 82, 182,182 a, 282, and 382 may comprise an anti-expulsion edge 8, 108, 108 a,208, and 308, for example, as shown in FIGS. 13A-13M.

The an anti-expulsion edge 8, 108, 108 a, 208, and 308 resists movementof the implant 1, 101, 101 a, 201, and 301 seated in the joint space ofthe spine. The anti-expulsion edge 8, 108, 108 a, 208, and 308 tends to“dig” into the vertebral end-plate bone, and thereby helps to resistexpulsion of the implant 1, 101, 101 a, 201, and 301 from theintervertebral space following implantation. The anti-expulsion edge 8,108, 108 a, 208, and 308 may be present on the top surface 10, 110, 110a, 210, and 310, the bottom surface 20, 120, 120 a, 220, and 320, orboth surfaces of the implant 1, 101, 101 a, 201, and 301, which maydepend on whether the implant 1, 101, 101 a, 201, and 301 includes anintegration plate 82, 182, 182 a, 282, and 382 attached to the topsurface 10, 110, 110 a, 210, and 310 and/or the bottom surface 20, 120,120 a, 220, and 320.

By way of example, FIG. 13A shows an anti-expulsion edge 8 on the topsurface 10 and bottom surface 20 and at the anterior face 40 of theimplant 1. Each anti-expulsion edge 8 protrudes above the plane of thetop surface 10 and bottom surface 20, with the amount of protrusionincreasing toward the anterior face 40 and the highest protrusion heightP at the anterior-most edge of the top surface 10 or bottom surface 20.As shown in FIG. 13B, the protruding anti-expulsion edge 8 exposes aprotruding surface 9.

An anti-expulsion edge 8, 108, 108 a, 208, and 308 may be orientedtoward the anterior portion 40, 140, 140 a, 240, and 340, or theposterior portion 50, 150, 150 a, 250, and 350, or either of theopposing lateral sides 30, 130, 130 a, 230, and 330. The orientation ofthe anti-expulsion edge 8, 108, 108 a, 208, and 308 may depend on theintended orientation of the implant 1, 101, 101 a, 201, and 301 when ithas been implanted between vertebrae in the patient.

FIGS. 13C-13H show different perspective views of different embodimentsof the implant 101 and 101 a, with the amount of protrusion increasingtoward the posterior face 150 and 150 a and the highest protrusionheight P at the posterior-most edge of the top surface 110 and 110 a orbottom surface 120 and 120 a. The protruding anti-expulsion edge 108 and108 a exposes a protruding surface 109 and 109 a. FIGS. 131-13K showdifferent perspective views of an embodiment of the implant 301, withthe amount of protrusion increasing toward one of the opposing lateralsides 330 and the highest protrusion height P at the most lateral edgeof the top surface 310 or bottom surface 320. The protrudinganti-expulsion edge 308 exposes a protruding surface 309. FIGS. 13L and13M show different perspective views of an embodiment of the implant201, with the amount of protrusion increasing toward the anteriorportion 240 and the highest protrusion height P at the anterior-mostedge of the top surface 210 or bottom surface 220. The protrudinganti-expulsion edge 208 exposes a protruding surface 209.

In some preferred embodiments, the integration plate 82, 182, 182 a,282, and 382 establishes the anti-expulsion edge 8, 108, 108 a, 208, and308 for either or both of the top surface 10, 110, 110 a, 210, and 310and bottom surface 20, 120, 120 a, 220, and 320 of the implant 1, 101,101 a, 201, and 301. Different integration plates 82, 182, 182 a, 282,and 382 may be used to establish a range of highest protrusion heightsP.

The integration plate 82, 182, 182 a, 282, and 382 has a thickness T,that is preferably substantially uniform throughout. Thus, for example,in embodiments where the integration plate 82, 182, 182 a, 282, and 382is substantially flush with the plane of the top surface 10, 110, 110 a,210, and 310 and/or bottom surface 20, 120, 120 a, 220, and 320 (e.g.,no protruding surface 9, 109, 109 a, 209, and 309) (e.g., FIG. 13N), therecess depth D in the implant body substantially corresponds to thethickness T of the integration plate 82, 182, 182 a, 282, and 382, andthe implant 1, 101, 101 a, 201, and 301 does not have the second recessdepth D′ (e.g., depth D is substantially uniform throughout).

In some embodiments, the integration plate 82, 182, 182 a, 282, and 382has a thickness T, that is preferably substantially uniform throughout,and the top surface 10, 110, 110 a, 210, and 310 and/or bottom surface20, 120, 120 a, 220, and 320 are recessed to a first depth D about oneportion and a second depth D′ about a second portion. For example, theposterior portion of the top surface 10, 110, 110 a, 210, and 310 and/orbottom surface 20, 120, 120 a, 220, and 320 may comprise a recess depthD, and the anterior portion of the top surface 10, 110, 110 a, 210, and310 and/or bottom surface 20, 120, 120 a, 220, and 320 may comprise thesecond recess depth D′. In such embodiments, when recess depth D isgreater than the second recess depth D′, the anterior portion 41, 141,141 a, 241, and 341 of the integration plate 82, 182, 182 a, 282, and382 will protrude to the height P. In such embodiments, when recessdepth D is lesser than the second recess depth D′, the posterior portion51, 151, 151 a, 251, and 351 of the integration plate 82, 182, 182 a,282, and 382 will protrude to the height P. In some aspects, one of thelateral portions of the top surface 10, 110, 110 a, 210, and 310 and/orbottom surface 20, 120, 120 a, 220, and 320 may comprise a recess depthD, and the opposing lateral portion of the top surface 10, 110, 110 a,210, and 310 and/or bottom surface 20, 120, 120 a, 220, and 320 maycomprise the second recess depth D′. In such embodiments, when recessdepth D is greater than the second recess depth D′, one of the lateralside portions 31, 131, 131 a, 231, and 331 of the integration plate 82,182, 182 a, 282, and 382 will protrude to the height P.

The recess depth D, the second recess depth D′, and the thickness T mayeach independently be from about 0.1 mm to about 10 mm. In preferredaspects, the recess depth D, the second recess depth D′, and thethickness T may each independently be from about 1 mm to about 5 mm.Thus, for example, the recess depth D, the second recess depth D′, andthe thickness T may independently be about 0.1 mm, about 0.25 mm, about0.5 mm, about 0.75 mm, about 1 mm, about 1.25 mm, about 1.5 mm, about1.75 mm, about 2 mm, about 2.25 mm, about 2.5 mm, about 2.75 mm, about 3mm, about 3.25 mm, about 3.5 mm, about 3.75 mm, about 4 mm, about 4.25mm, about 4.5 mm, about 4.75 mm, about 5 mm, 5.5 mm, about 6 mm, about6.5 mm, about 7 mm, about 75 mm, or about 8 mm.

The implant 1, 101, 101 a, 201, and 301 may comprise a lordotic angle.theta., e.g., may be wedge-shaped to facilitate sagittal alignment.Thus, for example, the anterior portion 40, 140, 140 a, 240, and 340 ofthe implant 1, 101, 101 a, 201, and 301 may comprise a height that islarger than the height of the posterior portion 50, 150, 150 a, 250, and350. The lordotic angle .theta. may be established by the implant 1,101, 101 a, 201, and 301 itself, or may be established by theintegration plate 82, 182, 182 a, 282, and 382 when combined with theimplant 1, 101, 101 a, 201, and 301.

The lordotic angle O of the implant 1 preferably closely approximates,or otherwise is substantially the same as, the angle of lordosis of thespine of the patient where the implant 1, 101, 101 a, 201, and 301 willbe implanted. In some aspects, the integration plate 82, 182, 182 a,282, and 382 increases the lordotic angle O by about 3% to about 5%,measured according to the angle of lordosis of a particular patient'sspine.

The implant 1, 101, 101 a, 201, and 301 may have a lordotic angle Oabout 3%, about 3.3%, about 3.5%, about 3.7%, about 4%, about 4.3%,about 4.5%, about 4.7%, or about 5% greater than the patient's angle oflordosis, though percentages greater than 5% or lesser 3% are possible.The increase of about 3% to about 5% preferably results from thecombination of the protruding height of the integration plate 82, 182,182 a, 282, and 382 on the top portion 10, 110, 110 a, 210, and 310 andbottom portion 20, 120, 120 a, 220, and 320 of the implant 1, 101, 101a, 201, and 301. For example, as shown in FIG. 14A and FIG. 14B, theanti-expulsion edge 8 protrudes to a height sufficient to increase theoverall height H of the anterior portion 40 of the implant 1 such thatimplant 1 has a lordotic angle O that is about 3% to about 5% greaterthan the patient's angle of lordosis. In this regard, the interplaybetween the depth D, the second depth D′, and the integration platethickness T, which together establish the protrusion height P establishthe lordotic angle O of the implant 1, 101, 101 a, 201, and 301.

The expulsion-resistant edge 8, 108, 108 a, 208, and 308 may comprise ananti-expulsion edge angle E. The anti-expulsion edge angle E may be fromabout 80 degrees to about 100 degrees. In preferred aspects, theanti-expulsion edge angle E may be measured by taking into account thelordosis angle O of the implant 1, 101, 101 a, 201, and 301. In highlypreferred aspects, the anti-expulsion edge angle E is measured bysubtracting half of the lordotic angle O from 90 degrees. For example,where the lordosis angle O of the implant 1, 101, 101 a, 201, and 301 is12 degrees, the anti-expulsion edge angle E is 84 degrees(90−(12.times.0.5)). The anti-expulsion edge angle E may be about 80degrees, about 81 degrees, about 82 degrees, about 83 degrees, about 84degrees, about 85 degrees, about 86 degrees, about 86.5 degrees, about87 degrees, about 88 degrees, or about 89 degrees.

The integration plate 82, 182, 182 a, 282, and 382 may be used with animplant suitable for ALIF (e.g., implant 1, integration plate 82), PLIF(e.g., implant 101, integration plate 182), or TLIF fusion (e.g.,implant 101 a, integration plate 182 a); may be used with an implantsuitable for cervical fusion (e.g., implant 201, integration plate 282);and may be used with an implant suitable for lateral lumbar insertion(e.g., implant 301, integration plate 382). The integration plate 82,182, 182 a, 282, and 382 is preferably metal, and may be used with ametal implant. The metal integration plate 82, 182, 182 a, 282, and 382may also be used with a molded plastic or polymer implant, or acomposite implant. In some aspects, the integration plate 82, 182, 182a, 282, and 382 may also comprise a plastic, polymeric, or compositematerial.

The reciprocal connector such as the post 84, 184, 184 a, 284, and 384preferably is secured within the connector of the body such as the hole12, 112, 112 a, 212, and 312 to mediate the connection between theintegration plate 82, 182, 182 a, 282, and 382 and the implant 1, 101,101 a, 201, and 301. The connection should be capable of withstandingsignificant loads and shear forces when implanted in the spine of thepatient. The connection between the post 84, 184, 184 a, 284, and 384and the hole 12, 112, 112 a, 212, and 312 may comprise a friction fit.In some aspects, an adhesive may be used to further strengthen any ofthe integration plate 82, 182, 182 a, 282, and 382 and implant 1, 101,101 a, 201, and 301 connections. An adhesive may comprise a cement,glue, polymer, epoxy, solder, weld, or other suitable binding material.

Vertebrae are comprised of trabecular bone of varying densities. Inopposition to the interbody disks this is thickened subchondral bone.Due to the lower density bone composition within the vertebral body loadinduced stresses can change the shape of the body. Movement, includingwalking, lifting, stretching, and other activities that implicatemovement and flexing of the spine produce load forces that impact discmaterial, and also induce flexing and compression of the vertebralendplate surfaces. For example, under load stress, the thickenedsubchondral bone of the vertebral endplate surface may flex inwardtoward the core of the vertebrae or outward toward the disc in theintervertebral space. Load forces and vertebral endplate bone flexingunder load forces may be taken into account in terms of theconfiguration of the implant 1, 101, 101 a, 201, and 301. A goal is tobalance the amount of surface area of the implant 1, 101, 101 a, 201,and 301 that contacts vertebral endplate surfaces so that the spine isadequately supported under load forces and stresses with the amount ofsurface area of bone graft material used in conjunction with the implant1, 101, 101 a, 201, and 301 to facilitate integration of the implant 1,101, 101 a, 201, and 301 and new bone growth.

For each implant 1, 101, 101 a, 201, and 301, the top surface 10, 110,110 a, 210, and 310 and/or bottom surface 20, 120, 120 a, 220, and 320make contact with the vertebral endplate bone, and surround the verticalaperture 60, 160, 160 a, 260, and 360 into which a bone graft materialis preferably placed and housed during implantation. When occupying thespace of the vertical aperture 60, 160, 160 a, 260, and 360, the bonegraft material also makes contact with the vertebral endplate bone. Inthis sense, portions of the top surface 10, 110, 110 a, 210, and 310and/or bottom surface 20, 120, 120 a, 220, and 320 and/or bone graftmaterial bear at least a fraction of the load forces and stresses of thespine where the implant is placed. The total load force or stress is notnecessarily borne equally by the implant surfaces and the bone graftmaterial, and is not necessarily distributed equally about the topsurface 10, 110, 110 a, 210, and 310 and/or bottom surface 20, 120, 120a, 220, and 320 of the implant 1, 101, 101 a, 201, and 301; certainsections, or subsections of the implant 1, 101, 101 a, 201, and 301 maybear a higher share of the load force relative to other sections.

To establish and maintain optimal contact between the implant surfaces,the bone graft material and the vertebral endplate bone, the location,direction, and extent, among other aspects, of flexing of vertebralendplate bone under load stress, and under normal conditions may betaken into account. Other factors such as the type of vertebrae betweenwhich the implant 1, 101, 101 a, 201, and 301 is/will be implanted(e.g., cervical, thoracic, lumbar), the specific vertebrae (e.g.,L-1/L-2 versus L-5/S-1) between which the implant 1, 101, 101 a, 201,and 301 is/will be implanted, the location where the implant 1, 101, 101a, 201, and 301 is/will be seated in the intervertebral space, the size,shape, and configuration of the implant 1, 101, 101 a, 201, and 301itself (including the dimensions, shape, and location of the verticalaperture 60, 160, 160 a, 260, and 360 and transverse rim), and theamount of disc material retained in the intervertebral space may also betaken into account. In addition, the direction of insertion, and theinsertion procedure (e.g., ALIF, PLIF, TLIF, etc.) may also be takeninto account.

For example, the practitioner may position the implant 1, 101, 101 a,201, and 301 in the intervertebral space at a loci where bone graftmaterial exposed through the vertical aperture 60, 160, 160 a, 260, and360 may make maximal contact with vertebral endplate bone, whether atrest/under normal conditions, or under particular load stress. Thepractitioner may also position the implant 1, 101, 101 a, 201, and 301in the intervertebral space at a loci where a higher amount of the loadstress will be borne by the posterior, anterior, or lateral portion ofthe top surface 10, 110, 110 a, 210, and 310 and/or bottom surface 20,120, 120 a, 220, and 320. By way of example, but not of limitation, FIG.15A shows the placement of the implant 1 in the intervertebral space(upper vertebrae not shown) on top of the apophyseal rim of the lowervertebrae endplate such that posterior portion 50 of the implant 1 ispositioned proximal to the posterior edge of the endplate. FIG. 15Bshows an anterior view of the example in FIG. 15A, with the implant 1between the upper and lower vertebrae. FIG. 15C shows the placement ofthe implant 301 in the intervertebral space (upper vertebrae not shown)on top of the apophyseal rim of the lower vertebrae endplate such that alateral side 330 of the implant 301 is positioned proximal to theposterior edge of the endplate and the anterior 340 and posterior 350portions of the implant 301 are positioned laterally. FIG. 15D shows ananterior view of the example in FIG. 15C, with the implant 301 betweenthe upper and lower vertebrae.

Numerous other positions of the implant 1, 101, 101 a, 201, and 301 inthe intervertebral space are possible. For example, as shown in FIG. 16Aand FIG. 16B, the practitioner may include two implants 101 in theintervertebral space (upper vertebrae not shown). In this non-limitingexample, the posterior portion 150 of each implant 101 faces theposterior edge of the endplate. Where two implants 101 are used, theimplants 101 may be positioned substantially parallel relative to eachother, or may be positioned at any suitable angle relative to eachother. In FIG. 16B, the arrows illustrate the direction in which theimplant 101 was inserted in a PLIF procedure.

A single implant 101 may be positioned at an oblique angle off of theanterior-posterior direction of the vertebrae, for example, as shown inFIG. 16C and FIG. 16D. A single implant 101 a that has a curved profilemay be positioned proximal to the anterior edge of the vertebralendplate, as shown in FIGS. 16E and 16F. The curvature of the implant101 may approximate the curvature of the vertebral endplate. The implant101 a may also be positioned proximal to the posterior edge of thevertebral endplate (not shown) or proximate to one of the lateral sidesof the vertebral endplate (not shown). The implant 101 a may also bepositioned more toward the center of the vertebral endplate, and lesstoward one of the edges of the vertebral endplate. The implant 101 a mayalso be positioned at an oblique angle off of the anterior-posteriordirection of the vertebrae.

The shape and configuration of the implant 1, 101, 101 a, 201, and 301itself may facilitate the goal of balancing the amount of surface areaof the implant 1, 101, 101 a, 201, and 301 and the amount of surfacearea of bone graft material that contact vertebral endplate bone. Insome aspects, the vertical aperture 60, 160, 160 a, 260, and 360 may belengthened and/or widened and/or positioned in different locations aboutthe top surface 10, 110, 110 a, 210, and 310 and/or bottom surface 20,120, 120 a, 220, and 320. For example, with respect to varying theposition, the vertical aperture 60, 160, 160 a, 260, and 360 may bepositioned substantially in the center of the body of the implant 1,101, 101 a, 201, and 301, or may be positioned off-center, such astoward the anterior 40, 140, 140 a, 240, and 340, or the posterior 50,150, 150 a, 250, and 350, or one of the lateral sides 30, 130, 130 a,230, and 330. The dimensions and location of the vertical aperture 60,160, 160 a, 260, and 360 may be based on the insertion path of theimplant 1, 101, 101 a, 201, and 301 and/or the final location andorientation in the disc space. The dimensions and location of thevertical aperture 60, 160, 160 a, 260, and 360 may also be based on thefrictional characteristics of the roughened surface topography 80, 180,180 a, 280, and 380.

In some aspects, the shape of the vertical aperture 60, 160, 160 a, 260,and 360 may be varied. For example, the shape may be substantiallycircular, elliptical, or D-shaped. In some aspects, the anterior,posterior, or lateral sides of the circle, ellipse, or D-shape may bowoutward (e.g., a rhomboid oval) or inward (e.g., hourglass shape). Theshape may also include straight edges, including a substantiallydiamond, triangular, rectangular, quadrilateral, or polygonal shape,including a star shape. The shape may comprise an irregular shape orform. The particular shape may be based on the insertion path of theimplant 1, 101, 101 a, 201, and 301 and/or the final location andorientation in the disc space. The shape of the vertical aperture 60,160, 160 a, 260, and 360 may also be based on the frictionalcharacteristics of the roughened surface topography 80, 180, 180 a, 280,and 380.

Thus, in some aspects, the shape, dimensions and location of thevertical aperture 61, 160, 160 a, 260, and 360 may be based on theinsertion path of the implant 1, 101, 101 a, 201, and 301 and/or thefinal location and orientation in the disc space. In some aspects, theshape, dimensions and location of the vertical aperture 60, 160, 160 a,260, and 360 may be based on the insertion path of the implant 1, 101,101 a, 201, and 301, and/or the final location and orientation in thedisc space, and/or the frictional characteristics of the roughenedsurface topography 80, 180, 180 a, 280, and 380.

In some aspects, the implant 1, 101, 101 a, 201, and 301 comprises anintegration plate 82, 182, 182 a, 282, and 382 on either or both of thetop surface 10, 110, 110 a, 210, and 310 and bottom surface 20, 120, 120a, 220, and 320, having a vertical aperture 61, 161, 161 a, 261, and361. Thus, the bone graft material is loaded into the vertical aperture61, 161, 161 a, 261, and 361 of the integration plate 82, 182, 182 a,282, and 382 and the vertical aperture 60, 160, 160 a, 260, and 360 ofthe implant 1, 101, 101 a, 201, and 301. Accordingly, bone graftmaterial housed in the implant 1, 101, 101 a, 201, and 301 may extendthrough the implant vertical aperture 60, 160, 160 a, 260, and 360 andthrough the integration plate vertical aperture 61, 161, 161 a, 261, and361. The surface of the graft material may thus establish, andpreferably maintain, contact the vertebral endplate bone.

As with the vertical aperture 60, 160, 160 a, 260, and 360, theintegration plate vertical aperture 61, 161, 161 a, 261, and 361 may belengthened and/or widened and/or positioned in different locations aboutthe top surface 81, 181, 181 a, 281, and 381 and/or bottom surface 83,183, 183 a, 283, and 383. For example, with respect to varying theposition, the vertical aperture 61, 161, 161 a, 261, and 361 may bepositioned substantially in the center of the integration plate 82, 182,182 a, 282, and 382, or may be positioned off-center, such as toward theanterior 41, 141, 141 a, 241, and 341, or the posterior 51, 151, 151 a,251, and 351, or one of the lateral sides of the integration plate 82,182, 182 a, 282, and 382. The dimensions and location of the verticalaperture 61, 161, 161 a, 261, and 361 may be based on the insertion pathof the implant 1, 101, 101 a, 201, and 301 and/or the final location andorientation in the disc space. The dimensions and location of thevertical aperture 61, 161, 161 a, 261, and 361 may also be based on thefrictional characteristics of the roughened surface topography 80, 180,180 a, 280, and 380.

In some aspects, the shape of the integration plate vertical aperture61, 161, 161 a, 261, and 361 may be varied. For example, the shape maybe substantially circular, elliptical, or D-shaped. In some aspects, theanterior, posterior, or lateral sides of the circle, ellipse, or D-shapemay bow outward (e.g., a rhomboid oval) or inward (e.g., hourglassshape). The shape may also include straight edges, including asubstantially diamond, triangular, rectangular, quadrilateral, orpolygonal shape, including a star shape. The shape may comprise anirregular shape or form. The particular shape may be based on theinsertion path of the implant 1, 101, 101 a, 201, and 301 and/or thefinal location and orientation in the disc space. The shape of thevertical aperture 61, 161, 161 a, 261, and 361 may also be based on thefrictional characteristics of the roughened surface topography 80, 180,180 a, 280, and 380.

Thus, in some aspects, the shape, dimensions and location of thevertical aperture 61, 161, 161 a, 261, and 361 may be based on theinsertion path of the implant 1, 101, 101 a, 201, and 301 and/or thefinal location and orientation in the disc space. In some aspects, theshape, dimensions and location of the vertical aperture 61, 161, 161 a,261, and 361 may be based on the insertion path of the implant 1, 101,101 a, 201, and 301, and/or the final location and orientation in thedisc space, and/or the frictional characteristics of the roughenedsurface topography 80, 180, 180 a, 280, and 380.

The implant vertical aperture 60, 160, 160 a, 260, and 360 preferablyaligns with the integration plate vertical aperture 61, 161, 161 a, 261,and 361. Thus each implant body vertical aperture 60, 160, 160 a, 260,and 360 and integration plate vertical aperture 61, 161, 161 a, 261, and361 preferably has substantially the same length, substantially the samewidth, substantially the same shape, and substantially the same locationon their respective surfaces.

Nevertheless, in some aspects, the integration plate vertical aperture61, 161, 161 a, 261, and 361 may be longer and/or wider and/orpositioned differently than its implant vertical aperture 60, 160, 160a, 260, and 360 counterpart. For example, the vertical aperture 60, 160,160 a, 260, and 360 may be narrower in terms of length and widthrelative to the integration plate vertical aperture 61, 161, 161 a, 261,and 361 (which are comparatively larger) such that the graft materialoccupies a wider surface area at its top or bottom relative to thecenter mass. Such a configuration may be desirable for purposes of usingless bone graft material by lessening the inner volume of the implant 1,101, 101 a, 201, and 301 to be filled with bone graft material. In thissense, the surface area of the bone graft material that will ultimatelycontact vertebral endplate bone is maximized (because the integrationplate vertical aperture 61, 161, 161 a, 261, and 361 has a largerberth), while the amount of bone graft material that does not contactvertebral endplate bone, but rather occupies space in the voids of theimplant 1, 101, 101 a, 201, and 301, is minimized (because the implantvertical aperture 60, 160, 160 a, 260, and 360 has a smaller berth). Forexample, the inner volume of the implant 1, 101, 101 a, 201, and 301 maycomprise a “V” shape, or an “X” or hourglass shape.

One or more of the anterior 40, 140, 140 a, 240, and 340 edges,posterior 50, 150, 150 a, 250, and 350 edges, and lateral side 30, 130,130 a, 230, and 330 edges of the implant may be rounded or tapered (see,e.g., FIG. 1A-FIG. 7). The rounding or tapering is preferably present onat least the insertion face of the implant 1, 101, 101 a, 201, and 301.The rounding or tapering may facilitate insertion of the implant 1, 101,101 a, 201, and 301 by lessening friction or the possibility of snaggingvertebral endplate bone as the implant 1, 101, 101 a, 201, and 301 isplaced and positioned in the intervertebral space. As well, the roundingor tapering may help to avoid snagging or damaging blood vessels andnerves in and around the insertion site.

The implant vertical aperture 60, 160, 160 a, 260, and 360 comprisesdimensions and a shape, and defines a transverse rim 100 (implant 1),200 (implant 101), 200 a (implant 101 a), 300 (implant 201), and 400(implant 301). The integration plate vertical aperture 61, 161, 161 a,261, and 361 comprises dimensions and a shape, and defines anintegration plate transverse rim 86 (implant 1), 186 (implant 101), 186a (implant 101 a), 286 (implant 201), and 386 (implant 301). Thetransverse rim 100, 200, 200 a, 300, and 400 is also defined by theposition of the implant vertical aperture 60, 160, 160 a, 260, and 360or the integration plate vertical aperture 61, 161, 161 a, 261, and 361(e.g., centered, toward the anterior edge, toward the posterior edge, ortoward one of the lateral edges) on the top surface 10, 110, 110 a, 210,and 310, the bottom surface 20, 120, 120 a, 220, and 320, or theintegration plate top surface 81, 181, 181 a, 281, and 381.

Each transverse rim 100, 200, 200 a, 300, and 400 and integration platetransverse rim 86, 186, 186 a, 286, and 386 comprise a posterior portionhaving a posterior portion width P, an anterior portion having ananterior portion width A, and a first lateral section having a firstlateral side width L, and a second lateral section having a secondlateral side width L′. For example, the posterior portion width P maycomprise the distance between the posterior edge of the implant 1, 101,101 a, 201, and 301 or posterior edge of the integration plate 82, 182,182 a, 282, and 382 and the posterior edge of the implant verticalaperture 61, 161, 161 a, 261, and 361 or the integration plate verticalaperture 60, 160, 160 a, 260, and 360. The transverse rim 100, 200, 200a, 300, and 400 or the transverse rim of the integration plate 86, 186,186 a, 286, and 386 effectively surrounds the vertical aperture 60, 160,160 a, 260, and 360 or 61, 161, 161 a, 261, and 361, respectively.

The transverse rim 100, 200, 200 a, 300, and 400 may be present on thetop surface 10, 110, 110 a, 210, and 310 and the bottom surface 20, 120,120 a, 220, and 320 of the implant 1, 101, 101 a, 201, and 301. Thetransverse rim of the integration plate 86, 186, 186 a, 286, and 386 maybe present on the top surface 81, 181, 181 a, 281, and 381 of theintegration plate 82, 182, 182 a, 282, and 382. The top surface 81, 181,181 a, 281, and 381 is the surface that is exposed and visible, and maymake contact with vertebral endplate bone. Thus, for example, the topsurface 81, 181, 181 a, 281, and 381 of an integration plate 82, 182,182 a, 282, and 382 that occupies the bottom portion 20, 120, 120 a,220, and 320 is the bottom-most surface of the implant 1, 101, 101 a,201, and 301. For clarification, the top surface of the bottomintegration plate is effectively the bottom surface of the implant.

The configuration of the implant vertical aperture 60, 160, 160 a, 260,and 360 and/or the integration plate vertical aperture 61, 161, 161 a,261, and 361 (e.g., the shape, dimensions, and position on the top orbottom surface) and the transverse rim 100, 200, 200 a, 300, and 400defined by the aperture shape, dimensions, and position distributes thespine load force (e.g., the downward force/stress that is produced bymovement of vertebrae from walking, lifting, moving, stretching,pushing, pulling, sitting, standing, jumping, laying supine, etc.) aboutthe implant 1, 101, 101 a, 201, and 301. The load force may changeand/or shift to different sections of the implant 1, 101, 101 a, 201,and 301 (e.g., posterior, anterior, or one of the lateral sides)depending on the type and/or direction of movement by the patient, aswell as the level of exertion underlying the movement, among otherthings.

The posterior portion width P may be about 1 mm to about 15 mm, about 1mm to about 7 mm, about 1 mm to about 6 mm, about 1 mm to about 5 mm,about 1 mm to about 4 mm, about 1 mm to about 3 mm, about 2 mm to about6 mm, about 2 mm to about 5 mm, about 2 mm to about 4 mm, about 2 mm toabout 3 mm, about 3 mm to about 8 mm, about 3 mm to about 7 mm, about 3mm to about 6 mm, about 4 mm to about 7 mm, about 4 mm to about 6 mm,about 5 to about 7 mm, or about 5 mm to about 6 mm. In some aspects, theposterior portion width P may be about 1 mm, about 2 mm, about 3 mm,about 4 mm, about 5 mm, about 6 mm, about 7 mm, about 8 mm, about 9 mm,about 10 mm, about 11 mm, about 12 mm, about 13 mm, about 14 mm, orabout 15 mm.

The anterior portion width A may be about 1 mm to about 15 mm, about 1mm to about 8 mm, about 1 mm to about 7 mm, about 1 mm to about 6 mm,about 1 mm to about 5 mm, about 1 mm to about 4 mm, about 1 mm to about3 mm, about 2 mm to about 10 mm, about 2 mm to about 9 mm, about 2 mm toabout 8 mm, about 2 mm to about 7 mm, about 2 mm to about 6 mm, about 2mm to about 5 mm, about 2 mm to about 4 mm, about 2 mm to about 3 mm,about 3 mm to about 10 mm, about 3 mm to about 9 mm, about 3 mm to about8 mm, about 3 mm to about 7 mm, about 3 mm to about 6 mm, about 3 mm toabout 5 mm, about 4 mm to about 9 mm, about 4 mm to about 8 mm, about 4mm to about 7 mm, about 4 mm to about 6 mm, about 5 to about 10 mm,about 5 mm to about 9 mm, about 5 mm to about 8 mm, about 5 mm to about7 mm, about 6 mm to about 8 mm, or about 6 mm to about 7 mm. In someaspects, the anterior portion width A may be about 1 mm, about 2 mm,about 3 mm, about 4 mm, about 5 mm, about 6 mm, about 7 mm, about 8 mm,about 9 mm, about 10 mm, about 11 mm, about 12 mm, about 13 mm, about 14mm, or about 15 mm.

The first lateral side width L and second lateral side width L′ may eachindependently be about 1 mm to about 10 mm, about 1 mm to about 9 mm,about 1 mm to about 8 mm, about 1 mm to about 7 mm, about 1 mm to about6 mm, about 1 mm to about 5 mm, about 1 mm to about 4 mm, about 1 mm toabout 3 mm, about 2 mm to about 10 mm, about 2 mm to about 9 mm, about 2mm to about 8 mm, about 2 mm to about 7 mm, about 2 mm to about 6 mm,about 2 mm to about 5 mm, about 2 mm to about 4 mm, about 2 mm to about3 mm, about 3 mm to about 10 mm, about 3 mm to about 9 mm, about 3 mm toabout 8 mm, about 3 mm to about 7 mm, about 3 mm to about 6 mm, about 3mm to about 5 mm, about 3 mm to about 4 mm, about 4 mm to about 10 mm,about 4 mm to about 9 mm, about 4 mm to about 8 mm, about 4 mm to about7 mm, about 4 mm to about 6 mm, about 5 to about 10 mm, about 5 mm toabout 9 mm, about 5 mm to about 8 mm, about 5 mm to about 7 mm, about 6mm to about 8 mm, or about 6 mm to about 7 mm. In some aspects, thefirst lateral side width L and second lateral side width L′ may eachindependently be about 1 mm, about 2 mm, about 3 mm, about 4 mm, about 5mm, about 6 mm, about 7 mm, about 8 mm, about 9 mm, or about 10 mm.

The posterior portion width P, anterior portion width A, first lateralside width L, and second lateral side width L′ may have the same sizerelative to each other, or may have a different size relative to eachother. When the position of the vertical aperture 60, 160, 160 a, 260,and 360 is positioned toward the anterior portion 40, 140, 140 a, 240,and 340, the anterior portion width A decreases and the posteriorportion width increases, relative to a comparable implant 1, 101, 101 a,201, and 301 in which the vertical aperture 60, 160, 160 a, 260, and 360is centered, and vice versa. When the position of the vertical aperture60, 160, 160 a, 260, and 360 is positioned toward a lateral side 30,130, 130 a, 230, and 330, the first lateral side width L (e.g., the sideto which the vertical aperture 60, 160, 160 a, 260, and 360 ispositioned closest) decreases and the second lateral side widthincreases, relative to a comparable implant 1, 101, 101 a, 201, and 301in which the vertical aperture 60, 160, 160 a, 260, and 360 is centered,and vice versa. The same holds true with respect to the positioning ofthe integration plate vertical aperture 61, 161, 161 a, 261, and 361.

The posterior portion width P, anterior portion width A, and/or firstand second lateral side width L and L′ may allow for better stresssharing between the implant 1, 101, 101 a, 201, and 301 and the adjacentvertebral endplates, and helps to compensate for the weaker posteriorendplate bone. In some aspects, the transverse rim 100, 200, 200 a, 300,and 400 has a generally large surface area and contacts the vertebralendplate. The transverse rim 100, 200, 200 a, 300, and 400 may act tobetter distribute contact stresses upon the implant 1, 101, 101 a, 201,and 301, and minimize the risk of subsidence while maximizing contactwith the apophyseal supportive bone. Some studies have challenged thecharacterization of the posterior endplate bone as weaker.

The posterior portion width P, anterior portion width A, and/or firstand second lateral side width L and L′ comprise dimensions of theimplant top surface 10, 110, 110 a, 210, and 310, the implant bottomsurface 20, 120, 120 a, 220, and 320, and/or the integration plate topsurface 81, 181, 181 a, 281, and 381. Measured from the edge of onelateral side 30, 130, 130 a, 230, and 330 to the edge of the otherlateral side 30, 130, 130 a, 230, and 330, the implant top surface 10,110, 110 a, 210, and 310, the implant bottom surface 20, 120, 120 a,220, and 320, and/or the integration plate top surface 81, 181, 181 a,281, and 381 may be about 5 mm to about 50 mm in width, and in someaspects may be about 7 mm to about 15 mm, about 8 mm to about 12 mm,about 9 mm to about 12 mm, about 9 mm to about 11 mm, about 10 mm toabout 20 mm, about 10 mm to about 18 mm, about 10 mm to about 17 mm,about 11 mm to about 19 mm, about 11 mm to about 17 mm, about 12 mm toabout 17 mm, about 12 mm to about 16 mm, about 15 mm to about 25 mm,about 15 mm to about 23 mm, about 16 mm to about 24 mm, about 16 mm toabout 23 mm, about 17 mm to about 24 mm, about 17 mm to about 23 mm,about 18 mm to about 22 mm, about 20 mm to about 25 mm, about 20 mm toabout 22 mm, about 30 mm to about 50 mm, about 30 mm to about 48 mm,about 30 mm to about 45 mm, about 30 mm to about 42 mm, about 31 mm toabout 45 mm, about 31 mm to about 43 mm, about 31 mm to about 41 mm,about 32 mm to about 42 mm, or about 32 mm to about 40 mm in width.Measured from the edge of one lateral side 30, 130, 130 a, 230, and 330to the edge of the other lateral side 30, 130, 130 a, 230, and 330, theimplant top surface 10, 110, 110 a, 210, and 310, the implant bottomsurface 20, 120, 120 a, 220, and 320, and/or the integration plate topsurface 81, 181, 181 a, 281, and 381 may be about 9 mm, about 10 mm,about 11 mm, about 12 mm, about 13 mm, about 14 mm, about 15 mm, about16 mm, about 17 mm, about 18 mm, about 19 mm, about 20 mm, about 21 mm,about 22 mm, about 25 mm, about 30 mm, about 31 mm, about 32 mm, about33 mm, about 34 mm, about 35 mm, about 36 mm, about 37 mm, about 38 mm,about 39 mm, or about 40 mm in width.

Measured from the edge of the posterior portion 50, 150, 150 a, 250, and350 to the edge of the anterior portion 40, 140, 140 a, 240, and 340,the implant top surface 10, 110, 110 a, 210, and 310, the implant bottomsurface 20, 120, 120 a, 220, and 320, and/or the integration plate topsurface 81, 181, 181 a, 281, and 381 may be about 10 mm to about 70 mmin length, and in some aspects may be about 10 mm to about 20 mm, about10 mm to about 18 mm, about 11 mm to about 19 mm, about 11 mm to about18 mm, about 11 mm to about 17 mm, about 12 mm to about 16 mm, about 18mm to about 34 mm, about 18 mm to about 32 mm, about 20 mm to about 34mm, about 20 mm to about 32 mm, about 20 mm to about 31 mm, about 20 mmto about 30 mm, about 20 mm to about 28 mm, about 20 mm to about 27 mm,about 21 mm to about 32 mm, about 21 mm to about 30 mm, about 21 mm toabout 28 mm, about 21 mm to about 27 mm, about 22 mm to about 32 mm,about 22 mm to about 31 mm, about 30 mm to about 70 mm, about 35 mm toabout 65 mm, about 38 mm to about 64 mm, about 38 mm to about 62 mm,about 38 mm to about 60 mm, about 39 mm to about 62 mm, about 39 mm toabout 61 mm, or about 40 mm to about 60 mm in length. Measured from theedge of the posterior portion 50, 150, 150 a, 250, and 350 to the edgeof the anterior portion 40, 140, 140 a, 240, and 340, the implant topsurface 10, 110, 110 a, 210, and 310, the implant bottom surface 20,120, 120 a, 220, and 320, and/or the integration plate top surface 81,181, 181 a, 281, and 381 may be about 9 mm, about 10 mm, about 11 mm,about 12 mm, about 13 mm, about 14 mm, about 15 mm, about 16 mm, about17 mm, about 18 mm, about 19 mm, about 20 mm, about 21 mm, about 22 mm,about 23 mm, about 24 mm, about 25 mm, about 26 mm, about 27 mm, about28 mm, about 29 mm, about 30 mm, about 31 mm, about 35 mm, about 40 mm,about 45 mm, about 55 mm, or about 60 mm in length.

The size and shape of the vertical aperture 60, 160, 160 a, 260, and360, as well as the integration plate vertical aperture 61, 161, 161 a,261, and 361 are carefully chosen to achieve a preferable designtradeoff for the particular application envisioned for the implant 1,101, 101 a, 201, and 301. The vertical aperture 60, 160, 160 a, 260, and360 or integration plate vertical aperture 61, 161, 161 a, 261, and 361preferably maximizes the surface area of the top surface 10, 110, 110 a,210, and 310, integration plate top surface 81, 181, 181 a, 281, and381, and/or bottom surface 20, 120, 120 a, 220, and 320, while at thesame time maximizing both the capacity for radiographic visualizationand access to the bone graft material. It is highly preferred that thebone graft material bear at least some of the load forces of the spineonce the implant 1, 101, 101 a, 201, and 301 is implanted.

The vertical aperture 60, 160, 160 a, 260, and 360, and the integrationplate vertical aperture 61, 161, 161 a, 261, and 361 each preferablycomprises a maximum width at its center. The width of the verticalaperture 60, 160, 160 a, 260, and 360, and the integration platevertical aperture 61, 161, 161 a, 261, and 361 may range from about 20%to about 80% of the distance between opposing lateral sides. In someaspects, the width ranges from about 40% to about 80% of the distancebetween the opposing lateral sides. In some aspects, the width rangesfrom about 50% to about 70% of the distance between the opposing lateralsides. In some aspects, the width ranges from about 50% to about 65% ofthe distance between the opposing lateral sides. In some aspects, thewidth ranges from about 60% to about 70% of the distance between theopposing lateral sides. In some aspects, the width ranges from about 55%to about 75% of the distance between the opposing lateral sides. In someaspects, the width ranges from about 60% to about 80% of the distancebetween the opposing lateral sides. In some aspects, the width is about40%, about 45%, about 50%, about 55%, about 60%, about 65%, about 70%,about 75%, about 80%, about 85%, or about 90% of the distance betweenthe opposing lateral sides. Preferably, the width of the verticalaperture 60, 160, 160 a, 260, and 360, or the integration plate verticalaperture 61, 161, 161 a, 261, and 361 comprises the dimension betweenthe lateral sides.

The length of the vertical aperture 60, 160, 160 a, 260, and 360, andthe integration plate vertical aperture 61, 161, 161 a, 261, and 361 mayrange from about 20% to about 80% of the distance between the anteriorand posterior edges. In some aspects, the length ranges from about 40%to about 80% of the distance between the anterior and posterior edges.In some aspects, the length ranges from about 50% to about 70% of thedistance between the anterior and posterior edges. In some aspects, thelength ranges from about 50% to about 65% of the distance between theanterior and posterior edges. In some aspects, the length ranges fromabout 60% to about 70% of the distance between the anterior andposterior edges. In some aspects, the length ranges from about 55% toabout 75% of the distance between the anterior and posterior edges. Insome aspects, the length ranges from about 60% to about 80% of thedistance between the anterior and posterior edges. In some aspects, thelength is about 40%, about 45%, about 50%, about 55%, about 60%, about65%, about 70%, about 75%, about 80%, about 85%, or about 90% of thedistance between the anterior and posterior edges. Preferably, thelength of the vertical aperture 60, 160, 160 a, 260, and 360, or theintegration plate vertical aperture 61, 161, 161 a, 261, and 361comprises the dimension between the anterior and posterior edges. Thesize of the length and the size of the width of the vertical aperture60, 160, 160 a, 260, and 360, or the integration plate vertical aperture61, 161, 161 a, 261, and 361 may vary independently of each other.

The implant top surface 10, 110, 110 a, 210, and 310, the implant bottomsurface 20, 120, 120 a, 220, and 320, the integration plate top surface81, 181, 181 a, 281, and 381, the vertical aperture 60, 160, 160 a, 260,and 360, and the integration plate vertical aperture 61, 161, 161 a,261, and 361 each independently comprises a surface area, e.g., that ofthe horizontal plane (foot print). The surface area of the implant topsurface 10, 110, 110 a, 210, and 310, and the implant bottom surface 20,120, 120 a, 220, and 320, including the integration plate top surface81, 181, 181 a, 281, and 381 may comprise the roughened surfacetopography 80, 180, 180 a, 280, and 380 (contact surface), the areacomprising rounded or tapered edges, if rounded or tapered edges arepresent, and the area occupied by the vertical aperture 60, 160, 160 a,260, and 360, or the integration plate vertical aperture 61, 161, 161 a,261, and 361.

The drawings show examples different possible sizes, shapes, andpositions of the vertical aperture 60, 160, 160 a, 260, and 360 andintegration plate vertical aperture 61, 161, 161 a, 261, and 361. Thedrawings simply illustrate various configurations, and are not to beconsidered limiting in any way.

The vertical aperture 60, 61 may comprise any suitable shape,dimensions, and position on the implant 1. For example, FIG. 17A showsthe vertical aperture 60, 61 substantially in the center of the implant1. FIG. 17B shows the vertical aperture 60, 61 with a wider length andwidth such that the posterior portion width P, anterior portion width A,first lateral side width L, and second lateral side width L′ arediminished relative to the embodiment shown in FIG. 17A. FIG. 17C showsan example of the vertical aperture 60, 61 positioned to a lateral sideof the implant 1. FIG. 17D shows an example of the vertical aperture 60,61 having a wider length and width, and positioned nearer to theanterior portion 40 of the implant 1.

The length and width of the vertical aperture 160 may be enlarged suchthat the vertical aperture 160 spans most of the surface area of the topsurface 110, or the vertical aperture 161 may be positioned toward theanterior portion 140. Such configurations, in addition to other possibleconfigurations, are shown from a top perspective in FIGS. 18A-18D. Forexample, FIG. 18A shows the vertical aperture 160, 161 substantially inthe center of the implant 101, though the anterior-most edge of theaperture 160, 161 is positioned more toward the anterior edge of theroughened surface topography 180 of the top surface 110. FIG. 18B showsthe enlarged vertical aperture 160, 161 that is also positioned nearerto the posterior portion 150. FIG. 18C shows a vertical aperture 160,161 having a smaller profile that is positioned proximate to theposterior portion 150. FIG. 180 shows a vertical aperture 160, 161having a smaller profile that is positioned nearer to the a lateral side130.

Similar to the embodiments shown in FIG. 18, FIG. 19 illustratesdifferent shapes and dimensions of the vertical aperture 160 a and 161 aof the curved implant 101 a. Although the implant 101 a curves, and thevertical aperture 160 a and 161 a has curved edges as well, it is notnecessary the outer arc of the implant 101 a curve and aperture 160 aand 161 a lateral curves are identical. The shape of the implant 101 aand the shape of the vertical aperture 160 a and 161 a may beindependent of each other.

FIG. 19A shows the vertical aperture 160 a, 161 a substantially in thecenter of the implant 101 a, though the anterior-most edge of theaperture 160 a, 161 a is positioned more toward the anterior edge of theroughened surface topography 180 a of the top surface 110 a.

FIG. 198 shows the enlarged vertical aperture 160 a, 161 a that is alsopositioned nearer to the posterior portion 150 a. FIG. 19C shows avertical aperture 160 a, 161 a having a smaller profile that ispositioned proximate to the posterior portion 150 a. FIG. 19D shows avertical aperture 160 a, 161 a having a smaller profile that ispositioned nearer to the a lateral side 130 a.

FIG. 20A shows the vertical aperture 260, 261 substantially in thecenter of the implant 201. FIG. 20B shows the vertical aperture 260, 261positioned nearer to the second lateral side. FIG. 20C shows a widervertical aperture 260, 261 positioned substantially in the center of theimplant 201. FIG. 20D shows the vertical aperture 260, 261 positionednearer to the posterior portion 250.

The vertical aperture 360 and 361 may be positioned substantially in thecenter of the implant 301. The centered configuration is shown from atop perspective in FIG. 21A. FIG. 21B shows the vertical aperture 360,361 positioned nearer to the anterior portion 350. FIG. 21C shows thevertical aperture 360, 361 positioned proximate to a lateral side 330.FIG. 21D shows an enlarged vertical aperture 360, 361 positionedsubstantially in the center of the implant 301.

Example Surgical Methods

The following examples of surgical methods are included to more clearlydemonstrate the overall nature of the invention. These examples areexemplary, not restrictive, of the invention.

Certain embodiments of the invention are particularly suited for useduring interbody spinal implant procedures currently known in the art.For example, the disc space may be accessed using a standard mini openretroperitoneal laparotomy approach. The center of the disc space islocated by AP fluoroscopy taking care to make sure the pedicles areequidistant from the spinous process. The disc space is then incised bymaking a window in the annulus for insertion of certain embodiments ofthe spinal implant 1 (a 32 or 36 mm window in the annulus is typicallysuitable for insertion). The process according to the inventionminimizes, if it does not eliminate, the cutting of bone. The endplatesare cleaned of all cartilage with a curette, however, and asize-specific rasp (or broach) may then be used.

Use of a rasp preferably substantially minimizes or eliminates removalof bone, thus substantially minimizing or eliminating impact to thenatural anatomical arch, or concavity, of the vertebral endplate whilepreserving much of the apophyseal rim. Preservation of the anatomicalconcavity is particularly advantageous in maintaining biomechanicalintegrity of the spine. For example, in a healthy spine, the transfer ofcompressive loads from the vertebrae to the spinal disc is achieved viahoop stresses acting upon the natural arch of the endplate. Thedistribution of forces, and resultant hoop stress, along the naturalarch allows the relatively thin shell of subchondral bone to transferlarge amounts of load.

During traditional fusion procedures, the vertebral endplate naturalarch may be significantly removed due to excessive surface preparationfor implant placement and seating. This is especially common where theimplant is to be seated near the center of the vertebral endplate or theimplant is of relatively small medial-lateral width. Breaching thevertebral endplate natural arch disrupts the biomechanical integrity ofthe vertebral endplate such that shear stress, rather than hoop stress,acts upon the endplate surface. This redistribution of stresses mayresult in subsidence of the implant into the vertebral body.

Preferred embodiments of the surgical method minimize endplate boneremoval on the whole, while still allowing for some removal along thevertebral endplate far lateral edges where the subchondral bone isthickest. Still further, certain embodiments of the interbody spinalimplant 1, 101, 101 a, 201, and 301 include smooth, rounded, and highlyradiused posterior portions and lateral sides which may minimizeextraneous bone removal for endplate preparation and reduce localizedstress concentrations. Thus, interbody surgical implant 1, 101, 101 a,201, and 301 and methods of using it are particularly useful inpreserving the natural arch of the vertebral endplate and minimizing thechance of implant subsidence.

Because the endplates are spared during the process of inserting thespinal implant 1, 101, 101 a, 201, and 301, hoop stress of the inferiorand superior endplates is maintained. Spared endplates allow thetransfer of axial stress to the apophasis. Endplate flexion allows thebone graft placed in the interior of the spinal implant 1 to accept andshare stress transmitted from the endplates. In addition, sparedendplates minimize the concern that BMP might erode the cancellous bone.

Certain embodiments of the interbody spinal implant 1, 101, 101 a, 201,and 301 may maintain a position between the vertebral endplates due, atleast in part, to resultant annular tension attributable to press-fitsurgical implantation and, post-operatively, improved osteointegrationat the top surface 10, 110, 110 a, 210, and 310; the bottom surface 20,120, 120 a, 220, and 320; or both surfaces.

Surgical implants and methods tension the vertebral annulus viadistraction. These embodiments and methods may also restore spinallordosis, thus improving sagittal and coronal alignment. Implant systemscurrently known in the art require additional instrumentation, such asdistraction plugs, to tension the annulus. These distraction plugsrequire further tertiary instrumentation, however, to maintain thelordotic correction during actual spinal implant insertion. If tertiaryinstrumentation is not used, then some amount of lordotic correction maybe lost upon distraction plug removal. Interbody spinal implant 1,according to certain embodiments of the invention, is particularlyadvantageous in improving spinal lordosis without the need for tertiaryinstrumentation, thus reducing the instrument load upon the surgeon.This reduced instrument load may further decrease the complexity, andrequired steps, of the implantation procedure.

Certain embodiments of the spinal implant 1, 101, 101 a, 201, and 301may also reduce deformities (such as isthmic spondylolythesis) caused bydistraction implant methods. Traditional implant systems requiresecondary or additional instrumentation to maintain the relativeposition of the vertebrae or distract collapsed disc spaces. Incontrast, interbody spinal implant 1, 101, 101 a, 201, and 301 may beused as the final distractor and thus maintain the relative position ofthe vertebrae without the need for secondary instrumentation.

Certain embodiments collectively comprise a family of implants, eachhaving a common design philosophy. These implants and the associatedsurgical technique have been designed to address at least the ten,separate challenges associated with the current generation oftraditional anterior spinal fusion devices listed above in theBackground section of this document.

Embodiments of the invention allow end-plate preparation withcustom-designed rasps. These rasps preferably have a geometry matchedwith the geometry of the implant. The rasps conveniently removecartilage from the endplates and remove minimal bone, only in thepostero-lateral regions of the vertebral end-plates. It has beenreported in the literature that the end-plate is the strongest inpostero-lateral regions.

After desired annulotomy and discectomy, embodiments of the inventionfirst adequately distract the disc space by inserting (throughimpaction) and removing sequentially larger sizes of very smoothdistractors, which have been size matched with the size of the availableimplant 1, 101, 101 a, 201, and 301. Once adequate distraction isachieved, the surgeon prepares the end-plate with a rasp. There is nosecondary instrumentation required to keep the disc space distractedwhile the implant 1, 101, 101 a, 201, and 301 is inserted, as theimplant 1, 101, 101 a, 201, and 301 has sufficient mechanical strengththat it is impacted into the disc space. In fact, the height of theimplant 1, 101, 101 a, 201, and 301 is preferably about 1 mm greaterthan the height of the rasp used for end-plate preparation, to createsome additional tension in the annulus by implantation, which creates astable implant construct in the disc space.

The implant geometry has features which allow it to be implanted via anyone of an anterior, antero-lateral, or lateral approach, providingtremendous intra-operative flexibility of options. The implant 1, 101,101 a, 201, and 301 has adequate strength to allow impact. The sides ofthe implant 1, 101, 101 a, 201, and 301 have smooth surfaces, includedrounded or tapered edges to allow for easy implantation and,specifically, to prevent binding of the implant 1, 101, 101 a, 201, and301 to soft tissues during implantation.

The invention encompasses a number of different implant 1, 101, 101 a,201, and 301 configurations, including a one-piece, titanium-onlyimplant and a composite implant formed of top and bottom plates(components) made out of titanium. The surfaces exposed to the vertebralbody are dual acid etched to allow for bony in-growth over time, and toprovide resistance against expulsion. The top and bottom titanium platesare assembled together with the implant body that is injection moldedwith PEEK. The net result is a composite implant that has engineeredstiffness for its clinical application.

It is believed that an intact vertebral end-plate deflects like adiaphragm under axial compressive loads generated due to physiologicactivities. If a spinal fusion implant is inserted in the prepared discspace via a procedure which does not destroy the end-plates, and if theimplant contacts the end-plates only peripherally, the central dome ofthe end-plates can still deflect under physiologic loads. Thisdeflection of the dome can pressurize the bone graft material packedinside the spinal implant, hence allowing it to heal naturally. Theimplant 1, 101, 101 a, 201, and 301 designed according to certainembodiments allows the vertebral end-plate to deflect and allows healingof the bone graft into fusion.

The top and bottom surfaces of the implant may be made out of titaniumand are dual acid etched. The dual acid etching process creates a highlyroughened texture on these surfaces, which generates tremendousresistance to expulsion. The width of these dual acid etched surfaces isvery broad and creates a large area of contact with the vertebralend-plates, further increasing the resistance to expulsion.

The implant 1, 101, 101 a, 201, and 301 according to certain embodimentsof the invention has a large foot-print, and offers several sizes.Because there is no secondary instrument required to maintaindistraction during implantation, all the medial-lateral (ML) exposure isavailable as implantable ML width of the implant 1, 101, 101 a, 201, and301. This feature allows the implant 1, 101, 101 a, 201, and 301 tocontact the vertebral end-plates at the peripheral apophyseal rim, wherethe end-plates are the strongest and least likely to subside.

Further, there are no teeth on the top and bottom surfaces (teeth cancreate stress risers in the end-plate, encouraging subsidence). Exceptfor certain faces, all the implant surfaces have heavily rounded edges,creating a low stress contact with the end-plates. The wide rim of thetop and bottom surfaces, in contact with the end-plates, creates alow-stress contact due to the large surface area. Finally, the implantconstruct has an engineered stiffness to minimize the stiffness mismatchwith the vertebral body which it contacts.

Even the titanium-only embodiment of the invention has been designedwith large windows to allow for radiographic evaluation of fusion, boththrough AP and lateral X-rays. A composite implant minimizes the volumeof titanium, and localizes it to the top and bottom surfaces. The restof the implant is made of PEEK which is radiolucent and allows for freeradiographic visualization.

Although illustrated and described above with reference to certainspecific embodiments and examples, the invention is nevertheless notintended to be limited to the details shown. Rather, variousmodifications may be made in the details within the scope and range ofequivalents of the claims and without departing from the spirit of theinvention. It is expressly intended, for example, that all rangesbroadly recited in this document include within their scope all narrowerranges which fall within the broader ranges. In addition, features ofone embodiment may be incorporated into another embodiment.

The invention claimed is:
 1. An interbody spinal implant, comprising: abody that is generally oval-shaped in transverse cross section, andcomprises a top surface, a bottom surface, a posterior portion, ananterior portion comprising a solid rear wall extending substantiallythe entire width and height of the body, a substantially hollow center,and a single vertical aperture extending from the top surface to thebottom surface, and having varying width and maximum width at itscenter, wherein a portion of the top surface of the body, is recessedand comprises a plurality of vertical holes along the periphery of thevertical aperture, and wherein the recessed portion of the top surfaceof the body has an anterior section corresponding the anterior portionof the body and a posterior section corresponding to the posteriorportion of the body; a first integration plate comprising a top surfacehaving a roughened surface topography adapted to grip bone and inhibitmigration of the implant, a bottom surface having a plurality ofvertical posts, opposing lateral sides, opposing anterior and posteriorportions, and a single vertical aperture extending from the top surfaceto the bottom surface of the integration plate, aligning with the singlevertical aperture of the body, and defining a transverse rim, whereinthe entire bottom surface of the first integration plate is insertedinto the recessed portion of the top surface of the body and theplurality of posts are inserted into the plurality of holes, therebyaffixing the first integration plate to the body; and optionally asecond integration plate comprising a top surface having a roughenedsurface topography adapted to grip bone and inhibit migration of theimplant, a bottom surface having a plurality of vertical posts, opposinglateral sides, opposing anterior and posterior portions, and a singlevertical aperture extending from the top surface to the bottom surfaceof the integration plate, aligning with the single vertical aperture ofthe body, and defining a transverse rim, wherein if the secondintegration plate is present, a portion of the bottom surface of thebody is recessed and comprises a plurality of vertical holes along theperiphery of the vertical aperture, the non-recessed portion of thebottom surface comprises a blunt and radiused portion, wherein therecessed portion of the bottom surface of the body has an anteriorsection corresponding the anterior portion of the body and a posteriorsection corresponding to the posterior portion of the body, and whereinthe entire bottom surface of the second integration plate is insertedinto the recessed portion of the bottom surface of the body and theplurality of posts are inserted into the plurality of holes, therebyaffixing the second integration plate to the body.
 2. The interbodyspinal implant of claim 1, wherein the body and the first integrationplate are each comprised of a metal, and if a second integration plateis present, the second integration plate is comprised of a metal.
 3. Theinterbody spinal implant of claim 1, wherein the body is comprised of anon-metal polymer and the first integration plate is comprised of ametal, and if a second integration plate is present, the secondintegration plate is comprised of a metal.
 4. The interbody spinalimplant of claim 3, wherein the non-metal polymer is selected from thegroup consisting of polyetherether-ketone, hedrocel, and ultra-highmolecular weight polyethylene.
 5. The interbody spinal implant of claim1, wherein the body is comprised of a composite of a metal and anon-metal polymer selected from the group consisting ofpolyetherether-ketone, hedrocel, and ultra-high molecular weightpolyethylene.
 6. The interbody spinal implant of claim 1, wherein atleast the anterior section of the recessed portion of the top surface ofthe body is recessed to a depth corresponding to the thickness of thefirst integration plate, and if the bottom surface of the body isrecessed, at least the anterior section of the recessed portion of thebottom surface of the body is recessed to a depth corresponding to thethickness of the second integration plate.
 7. The interbody spinalimplant of claim 6, wherein the posterior section of the recessedportion of the top surface of the body is recessed to a depthcorresponding to the thickness of the first integration plate, and ifthe bottom surface of the body is recessed, the posterior section of therecessed portion of the bottom surface of the body is recessed to adepth corresponding to the thickness of the second integration plate. 8.The interbody spinal implant of claim 7, wherein the posterior portionof the first integration plate has a greater thickness than thethickness of the anterior portion of the first integration plate, and ifa second integration plate is present, the posterior portion of thesecond integration plate has a greater thickness than the thickness ofthe anterior portion of the second integration plate.
 9. The interbodyspinal implant of claim 1, wherein the anterior section of the recessedportion of the top surface of the body is recessed to a first depth andthe posterior section of the recessed portion of the top surface of thebody is recessed to a second depth that is less than the first depth,and if the bottom surface of the body is recessed, the anterior sectionof the recessed portion of the bottom surface of the body is recessed toa first depth and the posterior section of the recessed portion of thebottom surface of the body is recessed to a second depth that is lessthan the first depth.
 10. The interbody spinal implant of claim 1,wherein the posterior portion of the first integration plate comprisesan anti-expulsion edge to resist pullout of the implant from the spineof a patient into which the implant has been implanted, and if a secondintegration plate is present, the posterior portion of the secondintegration plate comprises an anti-expulsion edge to resist pullout ofthe implant from the spine of a patient into which the implant has beenimplanted.
 11. The interbody spinal implant of claim 1, wherein theposterior portion of the first integration plate protrudes above theplane of a non-recessed portion of the top surface of the body, and if asecond integration plate is present, the posterior portion of the secondintegration plate protrudes above the plane of a non-recessed portion ofthe bottom surface of the body.
 12. The interbody spinal implant ofclaim 11, wherein a second integration plate is present and the implantcomprises a lordotic angle adapted to facilitate alignment of the spine.13. The interbody spinal implant of claim 1, further comprising bonegraft material disposed in the substantially hollow center of the bodyand adapted to facilitate the formation of a solid fusion column withinthe spine.
 14. The interbody spinal implant of claim 1, wherein theposterior portion of the first integration plate has a greater thicknessthan the thickness of the anterior portion of the first integrationplate, and if a second integration plate is present, the posteriorportion of the second integration plate has a greater thickness than thethickness of the anterior portion of the second integration plate. 15.An interbody spinal implant, comprising: a body that is generallybox-shaped in transverse cross section, and comprises a top surface, abottom surface, a posterior portion, an anterior portion comprising asolid rear wall extending substantially the entire width and height ofthe body, a substantially hollow center, and a single vertical apertureextending from the top surface to the bottom surface, and having varyingwidth and maximum width at its center, wherein a portion of the topsurface of the body, is recessed and comprises a plurality of verticalholes along the periphery of the vertical aperture, and wherein therecessed portion of the top surface of the body has an anterior sectioncorresponding the anterior portion of the body and a posterior sectioncorresponding to the posterior portion of the body; a first integrationplate comprising a top surface having a roughened surface topographyadapted to grip bone and inhibit migration of the implant, a bottomsurface having a plurality of vertical posts, opposing lateral sides,opposing anterior and posterior portions, and a single vertical apertureextending from the top surface to the bottom surface of the integrationplate, aligning with the single vertical aperture of the body, anddefining a transverse rim, wherein the entire bottom surface of thefirst integration plate is inserted into the recessed portion of the topsurface of the body and the plurality of posts are inserted into theplurality of holes, thereby affixing the first integration plate to thebody; and optionally a second integration plate comprising a top surfacehaving a roughened surface topography adapted to grip bone and inhibitmigration of the implant, a bottom surface having a plurality ofvertical posts, opposing lateral sides, opposing anterior and posteriorportions, and a single vertical aperture extending from the top surfaceto the bottom surface of the integration plate, aligning with the singlevertical aperture of the body, and defining a transverse rim, wherein ifthe second integration plate is present, a portion of the bottom surfaceof the body is recessed and comprises a plurality of vertical holesalong the periphery of the vertical aperture, the non-recessed portionof the bottom surface comprises a blunt and radiused portion, whereinthe recessed portion of the bottom surface of the body has an anteriorsection corresponding the anterior portion of the body and a posteriorsection corresponding to the posterior portion of the body, and whereinthe entire bottom surface of the second integration plate is insertedinto the recessed portion of the bottom surface of the body and theplurality of posts are inserted into the plurality of holes, therebyaffixing the second integration plate to the body.
 16. The interbodyspinal implant of claim 15, wherein the body and the first integrationplate are each comprised of a metal, and if a second integration plateis present, the second integration plate is comprised of a metal. 17.The interbody spinal implant of claim 15, wherein the body is comprisedof a non-metal polymer and the first integration plate is comprised of ametal, and if a second integration plate is present, the secondintegration plate is comprised of a metal.
 18. The interbody spinalimplant of claim 17, wherein the non-metal polymer is selected from thegroup consisting of polyetherether-ketone, hedrocel, and ultra-highmolecular weight polyethylene.
 19. The interbody spinal implant of claim17, wherein the posterior portion of the first integration plate has agreater thickness than the thickness of the anterior portion of thefirst integration plate, and if a second integration plate is present,the posterior portion of the second integration plate has a greaterthickness than the thickness of the anterior portion of the secondintegration plate.
 20. The interbody spinal implant of claim 15, whereinthe body is comprised of a composite of a metal and a non-metal polymerselected from the group consisting of polyetherether-ketone, hedrocel,and ultra-high molecular weight polyethylene.
 21. The interbody spinalimplant of claim 15, wherein at least the anterior section of therecessed portion of the top surface of the body is recessed to a depthcorresponding to the thickness of the first integration plate, and ifthe bottom surface of the body is recessed, at least the anteriorsection of the recessed portion of the bottom surface of the body isrecessed to a depth corresponding to the thickness of the secondintegration plate.
 22. The interbody spinal implant of claim 21, whereinthe posterior section of the recessed portion of the top surface of thebody is recessed to a depth corresponding to the thickness of the firstintegration plate, and if the bottom surface of the body is recessed,the posterior section of the recessed portion of the bottom surface ofthe body is recessed to a depth corresponding to the thickness of thesecond integration plate.
 23. The interbody spinal implant of claim 22,wherein the posterior portion of the first integration plate has agreater thickness than the thickness of the anterior portion of thefirst integration plate, and if a second integration plate is present,the posterior portion of the second integration plate has a greaterthickness than the thickness of the anterior portion of the secondintegration plate.
 24. The interbody spinal implant of claim 15, whereinthe anterior section of the recessed portion of the top surface of thebody is recessed to a first depth and the posterior section of therecessed portion of the top surface of the body is recessed to a seconddepth that is less than the first depth, and if the bottom surface ofthe body is recessed, the anterior section of the recessed portion ofthe bottom surface of the body is recessed to a first depth and theposterior section of the recessed portion of the bottom surface of thebody is recessed to a second depth that is less than the first depth.25. The interbody spinal implant of claim 15, wherein the posteriorportion of the first integration plate comprises an anti-expulsion edgeto resist pullout of the implant from the spine of a patient into whichthe implant has been implanted, and if a second integration plate ispresent, the posterior portion of the second integration plate comprisesan anti-expulsion edge to resist pullout of the implant from the spineof a patient into which the implant has been implanted.
 26. Theinterbody spinal implant of claim 15, wherein the posterior portion ofthe first integration plate protrudes above the plane of a non-recessedportion of the top surface of the body, and if a second integrationplate is present, the posterior portion of the second integration plateprotrudes above the plane of a non-recessed portion of the bottomsurface of the body.
 27. The interbody spinal implant of claim 26,wherein a second integration plate is present and the implant comprisesa lordotic angle adapted to facilitate alignment of the spine.
 28. Theinterbody spinal implant of claim 15, further comprising bone graftmaterial disposed in the substantially hollow center of the body andadapted to facilitate the formation of a solid fusion column within thespine.
 29. The interbody spinal implant of claim 15, wherein the bodycomprises a D-shaped box in transverse cross-section, wherein theanterior portion is curved and the posterior portion is substantiallyflat, thereby forming the D-shaped box.